For a combination of convenience, contact area and secure fit I like the BFA-style bananas, also known as Z-plugs. It's easy to adjust the tension, either tighter or looser depending on your binding posts, they're very quick to connect and disconnect, and the entire length and diameter of the plug makes contact with the inner surface of the binding post.
Audioquest makes a version of it and the Knukonceptz brand available online are good quality and inexpensive.
Audioquest makes a version of it and the Knukonceptz brand available online are good quality and inexpensive.