I, myself, use limewire for certain files, but I have friends who use emule because Asian oriented sites tend to prefer the program. I think that both programs are similar in speeds. If you really want fast speeds, I think you should use bittorrent.
As for the bittorrent applications, Azureus is a great bittorrent application for advanced users. Although, the addition of Vuze may have been a bit too much because Vuze is really just adding more bulk to a very bulky application. Azureus will consume a large part of your memory while it is open and running. I recently switched to utorrent, and although it does not beat Azureus in the looks category, it is definitely on par with Azureus in the capabilities. Another great thing about utorrent is that the size of the program is ridiculously small, so it is a amazing program to enjoy at very little cost.