6WD: Which wheels to power?

[Mr_I]

We are very tempted to use the 6WD base that came in the kit of parts (simplicity, cost, agility, it's here now, etc.). The KoP frame, however, only powers the center wheel. I understand that a bot built this way can work (since the center wheel is hopefully always touching the carpet), but we're wondering about powering all the wheels.

Is working the details of chaining all six wheels worth the effort? Will powering only the center wheels put us at a disadvantage (pushing, for example)?