Azureus is slightly more complicated but more powerful in terms of how you can configure.
Bitcomet is more user friendly but then you can't tweek as much.
Generally using a bittorrent client insted of anything else will keep the spyware away as long as you use you common sence when chosing links and such. At the end of the day much of this crap comes from people saying yes to random popups that look like an update or somthign similar or using random programs, its endless but in most case you can keep your system clean by reguly updating and sweeping with Ad-AwareSE
Also if you don't allready I highly recomend you using Firefox as your browser rather then internet explorer as its full of holes. Firefox stops over 90% of the annoying things that bug you when browsing.
Heres a few settings you can change on firefox to make it more efficient and faster. ->
http://www.freerepublic.com/focus/f-news/1299854/posts
and stay away from thoese porn sites!!!!