[msimon785]

Just within the FIRST manufacturer/reseller community, we have 2 fantastic grip options in terms of roller claws, both of which have been mentioned here. I have used the BaneBots wheels on DIY home-built robots before, and I cannot help but attest their capability. They have a decent coefficient of friction, and are sold in ideal sizes for small robot applications, or, in this case, the proven roller claw.
Additionally, never set aside the ubiquitous AM Plaction/Traction treads when looking for tread options. It suffices to say that nearly every FIRST team has at very least played around with the stuff, while most have left over stock in their storage rooms. It works. That's why AM chose it, among many alternatives, to sell to the FIRST community.
I think that in terms of a roller claw, both options are more than sufficient. If you are looking for the better CoF, definitely go with the AM Plaction treads. If you prefer simplified mounting and a very reliable functionality, then the BaneBots wheels might be a better choice.
Cost wise, you must keep in mind that to use the AM treads, you must also purchase wheels. It is also necessary to have riveting capabilities. If you were to choose the BB wheels, which may prove to be cheaper, you will probably need a lathe to turn the ends of the hex shaft, such that they can fit in what would probably be 3/8" bearings.
Either way, good luck on your bot renovation!