If you have not seen this article from Car and Driver, I recommend it before buying new set of wheels:

Effects of Upsized Wheels and Tires Tested - Tech Dept. - Car and Driver

 

Duh, it's physics at play! Great article but it's missing the science to it!

Thinner sidewalls allow for more direct road feel, less lag from steering inputs and less flex during cornering.

As far as size and weight goes:

The more the weight is pushed outwards from the center of Torque, the more force needs to be applied! Plus larger wheels themselves are heavier with tires being about the same weight!

For example 17's vs 18's:




Thus it's easy to see M*17^2 < M*18^2 where M is the mass of wheel and tire combo and I (the result) is MOMENT OF INERTIA IE TORQUE REQUIRED TO MOVE OBJECT.