Bitdefender was fine when I used it. One of the few problems I had was when it detected my sister USB flash drive as dangerous, it was a false positive, but I was able to quickly fix it.
As for the heaviness, you can read my post here
http://malwaretips.com/threads/what...efender-system-performance.38929/#post-316528
As for the heaviness, you can read my post here
http://malwaretips.com/threads/what...efender-system-performance.38929/#post-316528
If he simply wants the engine, then I recommend Emsisoft. Either way is fine.So I keep 360TS with its engine.