The LR's top speed is more than double the highest speed limit here; I'm not ever going to be going anywhere near that top speed. Nor do I intend to drag race, so I don't need that extra acceleration. And those nicer wheels lower the top speed, which is of interest to those who want the speediest, and are more susceptible to failure. Of all the things I could have done differently, getting the P is not one of them.
Top speed in stock form is more determined by the type of tire you have. The Performance with the 20 inch come with PS4S tires that can easily do 162mph but the 18 inch stock wheels shouldn't be taken to those speeds. Also, the 20 inch come with stiffer sidewalls which aid in high speed runs vs. the thicker but less stiff sidewalls you have on the 18s.