This is a bit hard to say actually, which is the best, all have their advantages and disadvantages. I have tested the first one was Gnotella that was over 2 years ago which had the same slow feeling as Limewire.
After Gnotella there was a quite long period with Bearshare started with version 2 i think it was and ended with version 4 i reckon this client have evolved very much in terms of implementing features, I liked the webpage feature, but sadly they removed that, Im a statistic freak so i must say i liked the webstats they have, however i would have liked to see a new implementation of the stats covering much more. Same goes with other clients as well. I though Bearshare using much resources like Memory and Swap and started to feel a bit bulky atleast for my quite old machine now. Then i have tested Gnucleus 1.8.* i some what liked the look out of this one, felt lean in terms of memory and swap, but it didnt work well here, i think you have to have a quite strong machine in order for gnucleus to strieve. Then we have Xolox 1.4* a very slim client in terms of look and feel, very good search and download. Have some question over the host connection and reach of network, nothing informativ is shown in this client everything is stripped bar naked

Have no extra features at all thou. Since a started to sniff on Java programming i wanted to test a client in Java so here we are now with Limewire 2.9.0
well what to say its not a speed racer exactly, but works quite well, spares in terms of look, their statistic is not fully of the kind i want.