I've used both kinds extensively (the small and large in Grimmlokk's link, although not those specific brands/models) and I definitely prefer the small, portable ones. It's nice to be able to pick it up and move it around as you move from room to room, or if you're in a large room, move it from next to the couch where you're sitting to the computer desk on the opposite wall. I'd never use one of the big radiator-looking ones again unless I knew I only wanted to heat that single room. The small ones obviously won't generate as much heat as the big ones, but I think that is counter-balanced by the fact that you can just plop it down right next to where you're sitting.