I've never noticed much of a functional differance between G-10 and Micarta, so I can't be much help there. Lots of people seem to like them though.
Carbon fiber is extremely light and strong, but it is brittle and can easily crack if dropped or impacted, so I wouldn't consider it to be ideal for a tough knife. If uncoated it scratches easily. It works well for lightweight structural members (on aircraft, for example) but on knives it is more of a decorative feature because of the way it catches and reflects light. Due to the high cost, there is also a bit of luxury appeal attached to carbon fiber, which is why some cars use imitation carbon fiber on the interior.
If you simply want the strongest handle material for a user knife I would recommend you look at Zytel and other FRNs. When combined with full steel liners, this is very strong and resistant both to bending and impact. Some people decry Zytel as feeling hollow or cheap, but that doesn't change the fact that it is light, chemicly stable, and virtually indestructable.