I have been using Gnome for about 2 years. I sometimes dabbed with KDE 3, but only on Desktops.
I used to get angry at how horribly fast my laptop would run out of battery power. I'd have to scramble to find the cord every 45 minutes (the laptop has always been this bad) even when just doing something as simple as running Firefox or chatting on Skype. I had to take my damn cord everywhere I went! My cord was plugged into the laptop 80% of the time. Then we got my mother a new MacBook for christmas... she runs for hours at a time without even thinking about recharging... it can last a full day if you aren't heavily using it, unlike my barely-an-hour laptop that is otherwise powerful.
So I decided to switch to KDE for some reasons. And I was pleasantly surprised that my laptop can run a *lot* longer unplugged. I've been sitting here for about 1 hour and 10 minutes now, and I still have 31% battery life left; and that's WITH desktop effects enabled, Firefox, Skype, Pidgin, OpenOffice running all at once. I don't use my cord nearly as often. It's faster too.
Is it just me or is KDE better at power saving? Is KDE more advanced than Gnome? Share your thoughts.
Note: I am on Linux Mint 8 using the kubuntu-desktop package.