Colsons vs. VersaWheels vs. Treaded Traction Wheels

[Osseus_Dominum]

It doesn't actually say on the product info pages on VexPro, but I suppose it's a safe assumption that the coefficient of friction is tested on FRC spec carpet. So given that all of the CoF values for these wheels are very similar (or identical), which is the best overall for traction? It seems to me that the VersaWheels and the Tread on the traction wheels should give more grip than a Colson with the full weight of a robot because the treads can dig into the carpet unlike the smooth surface of the Colson rubber. Since we don't know how these wheels were tested, it's possible that this wasn't even a factor when measuring the CoF because they may not have loaded the wheels enough. So which style of wheel (and tread) really offers more grip?

On a related note, I haven't seen anyone discuss wheel size when talking about traction. It seems to me that a bigger wheel should give more traction since there is a larger area of rubber contacting the carpet. What do you think?