Glad to see you already made your decision by testing both, so this information will be rhetorical at best.
KDE has been historically known for doing "latest and greatest" as far as features. They try to sit on the bleeding edge of their niche, that being GUIs for *nix.
Gnome is their opposite in a way, as Gnome has shown that they will not implement something into their GUI until it is for all intents and purposes, bug-free. This is not to say that bugs aren't present, but that they have a very long incubation time on anything they consider introducing.
It's two schools of thought, and neither is necessarily better, it's just about your needs and how you work.
When installing Mandrake, I've always chosen KDE because it seemed "smoother" to me, and I knew where everything was since the first time I tried it.
Don't forget that there are other window managers available, like BlackBox, Window Maker, and a ton of others that aren't as "heavy" as Gnome or KDE. Both KDE and Gnome are great for various reasons, but they are by no means the end-all be-all of window managers.
From what ive read, gnome is also good for people with diabilities (blindness), were it will make sounds, its very interesting. I dont know why, ive never met a blind techie, well not yet. KDE, is just good looking, Gnomes great too, but ive always went KDE my self. Please do not forget gnome is very cosimzable as previously mentioned.
I use both alternately. Overall, I think KDE is better, but I use GNOME once in a while because I get tired of KDE. From what I hear, GNOME is easier for people switching from Mac OS, whereas KDE is easier for people switching from Windows.
I've heard many recommendations that users start with KDE, then decide if they like GNOME better once they're more comfortable with Linux, and from my limited experience, I think this is the way to go.
GNOME seems to me to be more speedy, and less extras on it, whereas KDE seems to have more bells and whistles, such as Palm stuff and Games.
I usually install both, and go with GNOME. I think on my next box, however, I will go with KDE, because I want to do more different things with linux. I work with RedHat / Fedora systems.
But for strict performance over VNC, TWM still wins hands down.
I'm in line with Christian on this one. Maybe I'm just apathetic, but I don't care what WM I'm in. The main criteria I use is "Can I quickly open a terminal in it?" Most of the time, that means I just use the default WM of the distro. Since I'm running Debian quite a bit now, that usually turns out to be Gnome.
To throw in my US$.02 regardng VNC performance, I'm going to have to shoot for ion (http://modeemi.cs.tut.fi/~tuomov/ion/), because it uses almost NO resources. I think using top, I calculated that ion was using at most 300KB of RAM on my box, and that's running over a VNC connection. Out of all the WMs I've come across, that one is the best example of my "Can I quickly open a terminal in it?" need.