I've supported Dimensions, Optiplexes, Inspiron laptops and desktops, Minis, Studio laptops and desktops, XPS laptops and desktops, Latitudes, Vostro laptops and desktops, the occasional Precision laptop here and there, and that whacky awesome little Studio Hybrid thing. I bought a Vostro A90 as a toy (and it's a wonderful little toy!). I bought a Latitude as a computer.
To me, anything under 11" is a toy, anything over 15.4" is a portable desktop. In between, there's laptops.
Which you should get depends what you want it to do. I find a 13-14" laptop to be computing's sweet spot, no compromises from miniaturization nor excesses because it's big enough that it can be done.
Vostro A90, 16GB SSD, 2GB DDR2, US-INTL Keyboard, FreeBSD 7.2-STABLE
Latitude E6400N, 2.4GHz, 4GB, 320GB, Opensolaris 2009.06 updated to build 118 Dell Tech Support agent