I agree with the advice of try them both, but would add, try them all. I favor Gnome, because it seemed simpler to set up to me, and I really don't like the look of KDE, no matter what I do to it. That being said, neither fits my needs perfectly. My biggest complaint would be the file managers...I don't like konquerer or nautilis. Nautilis especially sucks. I really like GMC, but it doesn't seem to get along with any desktop (KDE or Gnome) if you run it in KDE, even with the --nodesktop command, it draws icons everywhere. When I run it in Gnome, it makes my desktop flaky.
There are also currently no KDE apps that I prefer. My key apps are: open office, mozilla, gaim, evolution, gimp, acroread, real player, and gnucash (although I think I am going to try codeweavers crossover with Quicken) and various games.