I use ACAD Lt - they do allow you to put a single copy on both your laptop and desktop, so I have it on both. I much prefer to use the desktop or a couple of reasons. The first is that I have it set up with two monitors which makes it easy for me to refer to other materials (site photos, an email, something from the internet, ...) as I draw. I also like having my desk set up where the keyboard is not attached to the monitor and I have a good gaming mouse instead of a finger pad on a laptop.
I have the laptop so that I can get work done when I'm not in my office or bring it on site (I rarely do either). I probably use the laptop more when I want to watch a football game on tv and get work done at the same time than I do on site. I do not like to use a computer when I present a plan - it makes some people think that the computer did it and makes me less important.
The laptop is also a great backup. I actually sat in my van working on a plan during a hurricane (weak one) while the power was out so that I had power for my laptop.