as for any program that has alternatives, like browsers, text editors, and firewalls, you have to use all of them and see which one suits you the best. I have used all of the BT clients except for bittornado or ones that have popped up recently. But I have always gone back to ABC cause of the advanced options and the small amount of resources it uses.
The main reason I love to use ABC is because when I am playing cz or cs 1.6 or cs source I can have ABC running in the background and have almost no problems whatsoever. that's why I will never use azureus...eventhough it's a good program it just takes up to many resources