Last I heard, Deluge was the preferred minimalist client. I've never noticed much difference between the ones I've tried other than that some have ads. Performance seems to be pretty much the same across the board.
I wouldn't called Deluge minimalist - that's Transmission.
Deluge is more of a power-tool, albeit one most people can use happily.
The big thing that I like is that you can use the desktop GUI (GTK) client with a remote daemon doing the actual downloading. Plenty of them have web-clients (Deluge does as well), but it's nice using the proper GUI. Other than that, it has all of the usual tools you'd want from a client.
