I've tried most of these clients, but I keep going back to the old uTorrent 2.2.1 (the newer versions are indisputably awful). I find that it still has the best UX to date. On nix machines I use qB.
Edit: Warning: newer versions of uTorrent are malware. I recommend people pick a different client, as uTorrent actively tries to trick people into downloading the newer versions.