The beauty of "lowest possible latency" is in the eye of the beholder.  
If you're monitoring via hardware... and that's the extent of your needs (low latency monitoring), then you're set.
However, if you're trying to do something like trigger drum samples from an electronic kit (and have them feel as immediate/responsive as possible), having lowest possible latency is a much bigger deal.
 
Playing live:
When you get fairly distant from a monitor speaker or the mains (say going well out into the audience without wearing in-ear-monitors), the latency can be huge/distracting.
Can you compensate?  Yes
Is it comfortable?  No
 
All audio interface drivers are NOT created equal.
ie: Presonus Audio Box and RME Fireface UFX can both be set to a 64-sample ASIO buffer size.  
Reported latency will indeed be similar.
Guess which one allows running heavier loads glitch-free?  
That's part of what you're paying for when buying an RME audio interface.
 
I know Aaron (spear-headed pooling the round-trip latency information in the link above).
He's a good guy... and certainly means well (to help other folks).
 
 

Thanks for that Jim. So I guess those figures are more or less accurate but they don't tell the whole story. 
Many were using Reapers report and just like Sonar they can only report what the driver tells them. 
 
I do play a digital drum kit and even at my lowest buffer setting ( 2ms Scarlett what ever that means) I can hear a digital delay if I monitor both the Brain and the VST. So I monitor the brain while tracking because fighting latency sucks. The odd thing is I have never noticed this while tracking Keyboard parts. I guess I'd hear it if my keyboard generated sound too. 
 
So maybe the lesson learned is RTL can be workable with most name brands of interfaces. How stable that is at low buffers is driver and CPU dependant. The top performers are more stable using the same CPU.
 
Low latency is not necessarily a sign of a good driver. 

Jim Roseberry
The beauty of "lowest possible latency" is in the eye of the beholder.  
If you're monitoring via hardware... and that's the extent of your needs (low latency monitoring), then you're set.
However, if you're trying to do something like trigger drum samples from an electronic kit (and have them feel as immediate/responsive as possible), having lowest possible latency is a much bigger deal.
 
Playing live:
When you get fairly distant from a monitor speaker or the mains (say going well out into the audience without wearing in-ear-monitors), the latency can be huge/distracting.
Can you compensate?  Yes
Is it comfortable?  No
 
All audio interface drivers are NOT created equal.
ie: Presonus Audio Box and RME Fireface UFX can both be set to a 64-sample ASIO buffer size.  
Reported latency will indeed be similar.
Guess which one allows running heavier loads glitch-free?  
That's part of what you're paying for when buying an RME audio interface.
 
I know Aaron (spear-headed pooling the round-trip latency information in the link above).
He's a good guy... and certainly means well (to help other folks).
 
 

THIS ^^^