[mahout]

You should know that its not only the weight of the wheels but also the weight of the tires and the radius of the weights.

When you put 205/50x15" tires with a diameter of 23.44" the weight of the tire is 21#. The wheel weight is 12.6 pounds. So the rotational deadweight is 12.6# at 5.5" and 21# at 11.7". The torque to rotate the wheel is 5.8 lbft + 20.5 lbft. The total torque resistance to turning is 26.3 lbft. However the main resistance is the tire at 20.5 lbft.

So lets put 17" wheels and 205/40x17 (23.44" diameter) tires on. The 17" wheel weighs 14 lb at 6.5" and the 17" tire weighs 19 lb at 11.7". That torque resistance is 7.6 + 18.5 lbft or 26.1 lbft.
Again the main resistance is the tire at 18.5 lbft.

In this case the 17" combo has less torque resistance than the 15" and therefore should accelerate faster with whatever torque the engine can develop. The less weight at the outside the easier you will accelerate the rotational speed.

Thanks to TireRack for tire specs and Grassroots Motorsports for wheel data (their ads list the wheel weights) - which vary all over the place so my little example isn't true for all combo tires/wheels. Generally it is because the tire weights are at the fartherest radius and that makes them controlling, generally.
This is not a real precise calculation as I really should calculate the centers of rotating mass to get a more accurate torque. However, past experience has shown that indeed the tire tread is pretty much the controlling factor. The beefier the tire the more weight and slower accelerating. And thats why usually when going to wider tires you try to reduce the outside diameter a wee bit to reduce the torque resistance. A wee bit, not a lot.
See, thats why you went to Physics and Math classes. My students had to solve equations like this. And why dished corners were faster than flat ones.
cheers.

PS its also why you want to remove all wheel weights BEFORE mounting new tires and balancing.
Leaving the on just adds to weight being turned.