The crazy bumpy roads in Calgary coupled with construction is why I chose the 19'' over the 21'' wheels. However, I do agree that the 21'' looks better. I decided that this would be my daily driver and main car, so opted for a little practicality to offset the completely impractical purchase of a 3.1s supercar to commute to work
Those who've seen the car think the wheels look awesome however. So I suppose the choice would be in the eye of the beholder. I would like to see what it feels like to ride with 21'' rims though, just because my 19'' wheels feel real smooth and comfy on the roads and there must be a difference.
The debate over 19" vs. 21" can be endless. It really depends on personal choice.
The 21" on a Tesla are definitely "low profile". Apparently not the best for winter and not the best for rough roads.
Will you be able to tell the difference in everyday driving? I'm skeptical.
With very limited experience so far with the Tesla (21" Winter, air suspension, 45psi now, not 40psi), it can feel smoother than what I experience with a 19" Porsche Cayenne (also air suspension).
I have recently blown a tire on the Cayenne (19") on the way to the airport. No idea what caused it, it went to the dealer within the hour and I caught the next flight. The Cayenne has brought me through some very deep snow without stress. Can the Tesla? I do not have the experience yet, but it is clearly not just a function of 19" vs. 21" (and this difference may be minimal). The actual tires and suspension height are probably the determining factor.
As mentioned earlier, you need to be concerned with curb damage to the rims with the 21" Tesla configuration (I can only speak to the winter configuration so far). Some tires have an extra rubber protrusion just above the rim so the rubber hits first before the rims get scraped. Not so on the winter configuration I received. So I need to be extra careful when parking against a curb (as mentioned by Han Chen).
I get the feeling that "chance / capability of the drive train / suspension system you have / software driving all the components / tire pressure" has more to do in this equation than just between 19" vs. 21" wheels. Eventually you will damage a tire and will eventually damage a rim in either case.
19" are less expensive. 21" "look better".
Does not answer your question, but hope this helps in a small way.