Once I hook up everything I like to use, extra monitor, keyboard, mixing monitors. It isn't worth it for me. Even though some of the older nagging issues have been solved to some extent like heat issues and performance issues .vs desktop. I prefer to stay with a desktop for ultimate flexibility. 
 
IF I had to choose a laptop for portability and transport reasons I would be looking at a highly spec'd model for gaming. Fast cpu, lots of memory, Good heat dissipation, low noise. Nice touch screen. A laptop would make a great second computer if I was on the road. You could use it in the motel room and do rough mixes on headphones.
 
If you're confined to a small space I get it. Not too many other options.You can spend as much or more on a high end laptop as a desktop though.Laptops aren't quite as configurable as a general rule.Especially when looking at hardware upgrades.
 
It sure looks as if the big computer manufacturers are attempting to move to portable everything. It's probably less expensive for them to make smaller less powerful units that will do the basic job. Even the office market is seeing plenty of unified setups. Either tiny outboard cubes or everything built into the monitor. The average Joe doesn't look too hard at specs. Their only concern is whether or not is will do the job.
 
Many of the videos Cake has put out use laptops as demo units. When they go to NAMM or similar they seem to be using lappys. Maybe they see a trend away from  desktops?
 
If it was all I had I would use a laptop. Until or unless that happens. It's a desktop for me. One I'll build.

I've been a laptop only use for getting on five years now.
 
When I want to do stuff in my "studio," which houses my hardware synths and what have you, I hook up to my OCTA-CAPTURE.
 
When I am out and about I take my QUAD-CAPTURE with me and I can set up virtually anywhere, even in my motorhome, which means I can be sat at the side of a lake in the middle on nowhere. Obviously I will be working "in the box" with all my VST instruments and effects.
 
Laptop wasn't cheap... And I have upgraded the SSD's since too, so I must have spent something like £3000 on my system, not including software.
 
Would I go back to a desktop?
 
Answer to that is no... Laptop suits my "limited" needs... I don't intend mic'ing up guitar amps and drum kits any more...

If I only worked at home I'd totally stick with a desktop. If I only occasionally recorded a vocal on the road or did a hotel room mix I'd still use a desktop for most stuff. As it is, I do lots of production in various studios where they have lots of equipment to hook up to. It's just easier to plug in my laptop and have everything ready to go. Once I had all my plugins installed and went to do production on site for days, and my laptop coping fine with everything, it became far less compelling to keep transferring everything back and forth between desktop and laptop, not to mention keeping track of "latest versions" etc. Far quicker to just plug in my soundcard, trackball and extra screen at home.

When I was migrating between laptop and desktop I used an external USB HD for projects hooked to an A/B switch so they were all in one place and easily accessible to both systems. But since X2 I've only used laptops. Current gaming laps are far and ahead of what they were even 5 years ago. I came across this one sort of by accident and seems to have everything I'd want in a big clunky desktop including 3 internal HDDs. AND I can take it with me! It even has an onboard SoundBlaster card incase I should ever need to access it.
 
I used to spend time building desktops the way I wanted them. It was fun but also time consuming and a distraction from the ultimate goal of using a DAW. Now I just buy laptops that work for me already made and ready to go. Honestly I've seen no real difference in performance or functionality.
 
What to do with those 3 desktops sitting around with no purpose just getting in the way?!
 
YMMV

Working with a desktop in the studio ( see specs in my signature)
and a laptop (HP probook 6450 b) as a mobile device I can say
that the videomonitor of a laptop is to small and uncomfortable imo,
but a  good laptop with a external video monitor woukd do the job for
me.
On the other hand :
Ther is 1  hd and 2ssds in my desktop which keep this system
since 4,5 years very powerdul.I don´t think that it has to be renewed
within the next 2 years , don´t know if a laptop is so resistant.
A desktop also means to be able to change components easy.
regards

laptop here, only issue is number of usb ports (never enough!)

Pragi
Working with a desktop in the studio ( see specs in my signature)
and a laptop (HP probook 6450 b) as a mobile device I can say
that the videomonitor of a laptop is to small and uncomfortable imo,
but a  good laptop with a external video monitor woukd do the job for
me.
On the other hand :
Ther is 1  hd and 2ssds in my desktop which keep this system
since 4,5 years very powerdul.I don´t think that it has to be renewed
within the next 2 years , don´t know if a laptop is so resistant.
A desktop also means to be able to change components easy.
regards

My laptop fits 2 M2 drives and two regular 2.5" drives internally. That's disregarding the eSata, Thunderbolt and USB3 ports it also has for external storage. It also has a 17" full HD screen, a HDMI port and two display ports. So as Jim alluded to in his very first post, there's a huge difference between off the shelf "multimedia" laptops or higher end custom builds. I would never want to rely on a generic multimedia laptop as my sole computer. With the custom build I have now, I found myself surprised that I really don't need a desktop anymore. I have one but it just sits there. It's enough of a pain to keep one system up and running with hundreds of plugins and pieces of software, let alone two. Plus it has a faster CPU than my desktop (i7 6700 vs i7 3xxx something) at the moment.

pwalpwal
laptop here, only issue is number of usb ports (never enough!)

Yeah... I forgot about that...
 
I have one USB2 port, which I use exclusive with my Q-C or O-C and a further 3 USB3 ports. If I am sat in my "studio" I have to use a USB hub into which I plug my external computer keyboard and mouse. That leaves a port for my MOTU micro lite and one for my USB controller keyboard.
 
I seem to manage but I do wish that I didn't have to use that hub...

I find no issues with a hub as long as my audio interface is not on it. Hub is for MIDI interface and peripherals - DVD, printer, HDDs, mobiles, etc.

I moved from desktop based for music to "everything music is in the laptop" about 5 years ago. A few upgrades like moving to giant, super-speedy internal SSD drives helped turn it into nirvana.

It is so freeing. I work on music way more now because I can detach from the main studio area and sit elsewhere as I need to and still work on various things musically. I can create stuff, or experiment around, in a coffee shop if I felt like it.

Then of course, plugged in to the main studio area with outboard gear, microphones and monitors I'm back to full studio mode.

I can't imagine not having a laptop as the primary for music production.