I have 20” wheels on my R Design and, combined with the relatively short wheelbase and high center of gravity of the XC40, I think they make the ride quality too harsh for Midwest roads.
Remember that the wheel size does not change the outer dimension of the tire much.. the diameter of the wheel and tire combined stays more or less the same. The larger the wheel, though, the thinner the tire. So there’s less rubber between you and the road; hence the bumpier ride for larger diameter wheels.
Larger wheels are also heavier, so tests have shown that cars with larger wheels are a little slower. As the earlier poster mentioned, there’s sort of a “sweet spot” of performance.
In addition to the wheel diameter, an important factor is the width of the tread footprint. The wider the tires, the less traction you’re going to have on anything but dry pavement. While not always true, larger diameter wheels are also usually also wider.
Tire brand and quality are arguably often more important factors than wheel dimensions when it comes to performance.
So in my opinion, larger diameter wheels are usually a matter of form over function. People buy them because they like how they look, not because they’ll really perform better.