I'll try to give you some suggestions, but I'll pass on the donuts... :p
Gnome - relatively fast, although there is some bloat present. Has a very "cute" look to it, and appeals to many people, although some find that it's too limited, and that KDE suits them better.
KDE - the biggest and most bloated desktop manager for Linux. It takes TONS of RAM, and you need speedy computer to run it. If Gnome was geared to look more like Mac, then KDE is more of a Windows-type interface. It's got lots and lots of stuff including cool themes, but you had better not be prepared for it to be super-speedy.
Enlightenment - A newer desktop manager. It's great in the sense that it's really fast, and not nearly as bloated as some of the other managers such as KDE or even Gnome. The interface was designed to keep the amount of buttons at a minimal, with contextual menus playing a large role. My biggest complaint: lack of themes. While there's lots of attractive themes for KDE and Gnome, you're hard-pressed to find a Vista look-a-like, or a really good Mac theme (there are some, but they're not that great). However, if you're not a really picky person about themes, you probably won't mind the selection.
Fluxbox - Fluxbox too, is streamlined so it runs way faster than Gnome or KDE. I can't quite remember if it's faster than Enlightenment. In any case, I've never tried it, so I can't quite give you a personal experience. However, it seems to have a similar idea as Enlightenment for keeping the interface minimal. It also appears that Enlightenment is more popular than Fluxbox, as there's 19 million hits for "Enlightenment" on Google, compared to the meger 2 million hits for "Fluxbox".
I would suggest KDE if you have a powerful computer and want a complex, powerful environment, even if it isn't streamlined. If you like Mac's look, then Gnome might be your style. For absoloute speed, I would recommend Enlightenment.
Hope this helps