Vuze bloated and slow-moved from comments

I have used both of those clients extensively for about 2 years and have found no difference in speed.
Vuze uses more memory than uTorrent, but with a GB of RAM or more it is not an issue at all.

uTorrent is the best basic bittorrent client there is because of its small size (.21MB installed) and small memory use (944K), but Vuze keeps coming up with innovations that put it ahead.
The Vuze platform and the friends feature, which allows for totally encrypted transfer, are what put Vuze ahead now.
Although Vuze uses more RAM than most all bittorrent clients, its developers have reduced its memory usage about 1/3rd over the last year or so, while adding new features.

BTW, all the clients I tested, after proper setup, downloaded at basically the same speeds.