All other factors being the same (ie wheel and tyre width, type of tyre, etc. and ultimate tyre rolling radius) then I would expect larger rims to primarily:
1) give a harsher ride as they have a smaller sidewall to compress and act as a part of the suspension
2) improved grip as the same smaller sidewall flexes less and therefore keeps the tread flat
Problem is that when people change from 1 size rim to a larger they likely change tyre brands, rim width, offset, rolling radius, weight of wheel/tyre and where that it is in relation to the wheel centre and numerous other factors that can make countless new characteristics appear. The end result can be different acceleration, braking, cornering, tramlining, ride quality and many more factors that few ever consider, but they often look great
I know much of this from bitter experience of running Jeeps on 29", 31", 33" and 35" tyres all on 15" rims. Alloy rims, steel rims, Radial and crossply tyres. AT, MT and snow. Until I hit the road at 70MPH. I rarely have any idea if the Jeep will even be driveable without changing gear ratios and many other suspension dynamics.
Sorry - a long answer, but it is a complex subject
and don't tell me the answer is 2"(!) but apart from the 18" alloys looking nicer, how do each of them feel while driving? What are the advantages and disadvantages of both? Thanks!!
Low proflies and bigger rims will typically equal the original rolling distance provided the overall diameter matches the original? If you know what I mean. Debate :roll: