As already stated there's a ton of info previously posted on this, but mug of coffee in hand I will add my 0.02...
I work for an alloy wheel company and have an opinion that might run contrary to many of my colleagues. I'm actually a minimalist when it comes to diameter, I say run the smallest that will achieve the level of handling and appearance that you desire. The reasons are very simple: smaller diameter equals lighter weight. As a general rule of thumb, every pound you shave from the wheel (especially in the extremities like the rim barrel) will give you the same performance benefit as removing two pounds of dead weight from the body/chassis due to the reduced inertia. Of course you can find 19" flow formed or forged wheels that will be lighter than 17" cast ones, but then 17" flow-formed or forged ones are lighter than 17" cast ones, etc.
There's also the matter of ride, and of course the taller tire that goes with a smaller diameter wheel will in general have better ride characteristics and offer better protection against impacts. It will often - although not exclusively - offer lower rolling resistance.
On the downside, the taller tire will flex more and so have slower steering input response and usually less ultimate grip in dry cornering conditions.
Car and Driver in conjunction with Tire Rack did what I consider to be one of the definitive pieces on the whole subject:
Effects of Upsized Wheels and Tires Tested - Tech Dept.
My rule-of-thumb:
If you check mostly the following boxes:
Drive moderately / Live in pothole country / Want smoothest ride / Don't obsess over wheel appearance / Want to maximize range / Plan to run same wheels all year round (if living in variable climate)
- Get the smaller diameter
If you check mostly the following boxes:
Drive in "spirited" fashion / Live in a well maintained road area / Less concerned about ride / Like the sporty big wheel looks / Don't mind a little range sacrifice / Plan to run different winter wheels (if living in variable climate)
- Get the bigger diameter
Notice I leave wear out of the equation. Although it's true that as a rule lower profile tires wear quicker, there are now many 45 and lower series replacement models that offer 500+ tread wear ratings, so this is becoming less of a factor. And even if you pick the taller OEM size from the factory there's no guarantee they'll last a lot longer, OEM tires of all sizes are notorious for wearing quickly as the emphasis is on getting the desired performance, wear tends to come last.
Of course you might have checked boxes from both scenarios, in which case you can often find a happy marriage in an intermediate size. Say Tesla winds up offering a base 17" and a premium 19", there's nothing that prevents you from splitting the difference and going with an 18" package sourced from the aftermarket (flipping your OE setup to subsidize).
You can also play with the variables within a given diameter, like ordering the 19" setup but choosing a more comfortable and longer wearing replacement tires (flipping your OE setup to subsidize).
On my current A4 I downsized from the OE S-line 18" wheels and 235/40 tires to lightweight 17" with good 235/45 performance tires and I LOVE how it improved acceleration and braking while giving up very, very little in dry road performance, and it drives far better on our bomb-cratered Quebec roads.
Hope that helps shed a little more light.
