Arg, posting at work the worthless software known as internet explorer ate my post.
What I was saying was my preference is laptop unless your into always swapping hardware around. Just be careful that some of the low end consumer laptops are desktop replacements and can't really be used on a lap so if your looking at one of those then you may as well just get a desktop.
We just replaced both our laptops with smaller netbooks, much more handy to show years worth of pictures, small enough to go anywhere.