One way to look at it is that it takes more power to GET heavier tires moving. (Accelerate).With the 8spd auto, definitely weight. The trans can do an amazing job in making up for the change in effective gearing, but it just takes more power to get heavier tires moving. Look for light wheel/tires, unless you're planning to re-gear. This will help with ride, too.
And it takes more power to KEEP bigger tires moving. (Steady state)
Weight impacts acceleration and deceleration. Size impacts steady state resistance. Generally speaking.