It depends on where you want to use it as well.......
Visits to some of my more remote customers takes me on trips across (the Namib) desert and some very rough terrain. The conditions I work in are often very dusty, dry and hot. For years I used a Panasonic 'toughbook' recomended by an old Army buddy, but when this finally needed replacing, and because I wanted to upgrade to a newer spec, I looked around for some alternatives. I decided on a GETAC B300, which is another very rugged machine, built around a magnesium alloy case and has a shock-mounted hard drive, sealed I/O caps and doors etc, but what really sold it to me is its (optional) sunlight readable display - great for use outdoors in an African environment. So that's my ideal portable machine today, so far performing fantastically and even when my Jeep bounces over the harshest of ground I don't worry that my laptop will give up on me when I need it most - ie when I get to my customer!
So my advice is simply to go with what suits the conditions you are going to be using it in and even though you probably wont need anything as tough as the GETAC you might want to think about the times you are going to chuck the machine and its bag into the boot of the car along with all your other gear. As a road warrior who needs to rely on things working when you get to your destination, sometimes 'rugged' is better than very 'top end performance' - but of course its your choice!