usa423
My thoughts is USB interfaces are really only convenient. In my experience any professional audio internal CARD is much more pro...cleaner sound...more stable...etc etc.  But there are times when one cannot upgrade to a card. Such as a laptop.  At the end of the day it doesn't matter what you use as long as it has the features you need to DO what you need to do.  
 
I would stay away from any usb interface (or firewire) that doesnt offer ZERO LATENCY hardware monitoring.    

Internal PCI audio cards do not offer inherently cleaner sound nor do they offer greater stability. In fact, A/D converters placed inside the computer must take far greater care in shielding to ensure lack of interference. Of course it's entirely possible to design although more difficult and/or expensive. The sound quality of A/D devices placed outside of the computer, regardless of how they interface with the computer (PCI, FW, USB) is purely determined by the quality of components and the design of the circuitry. The interface itself is inconsequential. 

The bottom line here frankly is that "it doesn't really matter" - as long as certain factors are accounted for. If you've got a compatible FW chipset and audio device and you won't be swapping computers or laptops regularly then FW is just fine. If you need more widespread compatibility with multiple computers, then USB might have an advantage. But either way, both interface types will allow for enough track count and resolution to cover the needs of most users, except for those recording very high track counts at higher than average resolution.
 
This is good news for all of us. It means that basically most interface types will work just fine. So what it comes down to is driver stability, latency performance, how suitable the I/O array is for your particular needs, and price.
 

Brandon Ryan [Roland]

usa423
My thoughts is USB interfaces are really only convenient. In my experience any professional audio internal CARD is much more pro...cleaner sound...more stable...etc etc.  But there are times when one cannot upgrade to a card. Such as a laptop.  At the end of the day it doesn't matter what you use as long as it has the features you need to DO what you need to do.  
 
I would stay away from any usb interface (or firewire) that doesnt offer ZERO LATENCY hardware monitoring.    

Internal PCI audio cards do not offer inherently cleaner sound nor do they offer greater stability. In fact, A/D converters placed inside the computer must take far greater care in shielding to ensure lack of interference. Of course it's entirely possible to design although more difficult and/or expensive. The sound quality of A/D devices placed outside of the computer, regardless of how they interface with the computer (PCI, FW, USB) is purely determined by the quality of components and the design of the circuitry. The interface itself is inconsequential. 

In 2013 yes its finally a level playing field. Now say all that what you just said 10 years ago and keep telling yourself its the truth.  As I said "In my experience".   A usb interface TODAY is much different then the external interfaces of years ago.  I am just speaking what I know personally.

usa423

Brandon Ryan [Roland]

usa423
My thoughts is USB interfaces are really only convenient. In my experience any professional audio internal CARD is much more pro...cleaner sound...more stable...etc etc.  But there are times when one cannot upgrade to a card. Such as a laptop.  At the end of the day it doesn't matter what you use as long as it has the features you need to DO what you need to do.  
 
I would stay away from any usb interface (or firewire) that doesnt offer ZERO LATENCY hardware monitoring.    

Internal PCI audio cards do not offer inherently cleaner sound nor do they offer greater stability. In fact, A/D converters placed inside the computer must take far greater care in shielding to ensure lack of interference. Of course it's entirely possible to design although more difficult and/or expensive. The sound quality of A/D devices placed outside of the computer, regardless of how they interface with the computer (PCI, FW, USB) is purely determined by the quality of components and the design of the circuitry. The interface itself is inconsequential. 

 
In 2013 yes its finally a level playing field. Now say all that what you just said 10 years ago and keep telling yourself its the truth.  As I said "In my experience".   A usb interface TODAY is much different then the external interfaces of years ago.  I am just speaking what I know personally.

With regards to sound quality, it doesn't matter if it's 2013 or 2003. PCI interfaces do not currently, nor have they ever, inherently offered "cleaner" sound than USB or FW interfaces. In earler days, PCI and PCIe interfaces offered lower latency than their external counterparts, but not cleaner sound. Let's not conflate performance and sound quality - that's all I'm saying.
 
For instance, A Lynx Aurora can interface with the computer via PCIe or via optional FW add-on card. Regardless of which way it interfaces, the sound quality is identical.

Did Brandon just say I have to use a Lynx Aurora?
 
I can't wait for Xmas!!
 

Brandon Ryan [Roland]
 
With regards to sound quality, it doesn't matter if it's 2013 or 2003. PCI interfaces do not currently, nor have they ever, inherently offered "cleaner" sound than USB or FW interfaces. In earler days, PCI and PCIe interfaces offered lower latency than their external counterparts, but not cleaner sound. Let's not conflate performance and sound quality - that's all I'm saying.
 
For instance, A Lynx Aurora can interface with the computer via PCIe or via optional FW add-on card. Regardless of which way it interfaces, the sound quality is identical.

Oh now you tell me. So my 24 carrot gold diamond studded USB cable, made on the international space station by well trained monkeys, which I bought for $210,000 from Snakes R Us isn't giving me the audio quality I'm expecting ;)

I bought a saffire intending to use it with a PC laptop for live performance of vst's. I bought a firewire converter for an input that was designed to interface cameras on the laptop. The results were undependable. Sometimes it would just stop. I could reboot and get it working again.
The latency was very fast though. I ended up giving the saffire to my son. He has a Mac. He has had no trouble with it and is very happy with it.
 
Then I bought a saffire 6 USB for the PC laptop. It was dependable but the latency was noticeably worse. It went from 5 ms with the firewire to about 25 ms with the USB.
 
Now these both use the midi protocol. I don't know why firewire would have faster response than USB 2.0, but it does. If you are only using it for recording, more latency may be fine. Maybe USB 3.0 will not solve the latency problem. I see thunderbolt available now for PC motherobards. There are thunderbolt audio interfaces available too. It is reported to be five times faster than firewire. Strangely, there are no USB 3.0 audio interfaces and no USB 3.0 keyboards. Thunderbolt for audio is reported to be limited to a select few musicians with bags of money to throw at new gear.
 
I gave up on live performances with the band, because the latency was so terrible.
 
I heard that some PC motherboards that feature firewire are dependable. Some that use a different chipset are not.
 
Could it be that firewire converts midi data into a different, faster protocol and reconverts it back when it has to?
 

corgidaddy
 
 
Then I bought a saffire 6 USB for the PC laptop. It was dependable but the latency was noticeably worse. It went from 5 ms with the firewire to about 25 ms with the USB.
 
Now these both use the midi protocol. I don't know why firewire would have faster response than USB 2.0, but it does. If you are only using it for recording, more latency may be fine.  
?

What happened, when you lowered the latency settings using the USB 2?
People have been using USB 2 interfaces with under 5 ms latency for a long time, and 25 ms latency was much already ten years ago, so I doubt this was a USB/FW -issue per se (?).
AFAIK, most of the latency usually comes from the actual processing of the signal (>soft synths, amp sims), not from transferring it.

Sorry if someone already mentioned these but, some things to look out for:
 
1. USB2 devices will not always work with a USB3 source. (My laptop has 1 USB2 and 3 USB3 ports. My interface is USB2 and will not work with the USB3 ports which leaves only one port dedicated to it.)
 
2. If you plan on using a HUB to rout several devices to your system, make sure it is powered by house current. Even then your DAW will not always see the interface.
 
3. Some interfaces have iffy drivers. Make sure your unit has the latest. At one point MOTU had drivers that did not behave right but they soon replaced them with good ones.
 
Steve

Some random factoids...
 
FireWire has hardware to take over certain tasks, USB uses the CPU. This made a difference with older CPUs, but is no longer really relevant.
 
FireWire 800 is much faster than USB 2.0. FireWire 400's bandwidth is theoretically lower than USB 2.0, but the practical difference is negligible and FW 400 can outperform USB 2.0 by a very slim margin under some conditions.
 
FireWire dates from 1984, so it's a pretty old protocol. FireWire devices will work with Thunderbolt via an adapter, although not all PCIe devices will.
 
FireWire can be pickier than USB in terms of hardware, but if you get it working initially, it will pretty much stay working.
 
Don't expect to see a flurry of USB 3.0 interfaces. USB 2.0 covers most applications, and for really hardcore pro applications, companies will skip directly to Thunderbolt.
 
Virtually anything will work if you don't need a lot of I/O.
 
FireWire is no longer being included in many Windows laptops, and these laptops also don't have a card slot for adding a FireWire PCMCIA-type interface.
 
Tests based on copying files via one interface or another do not necessarily mean you'll achieve the same results with audio.