Yeah with the hill we live on, mine won't see the light of day with any hint of frost, snow or ice. Most likely settle for the all-seasons. Though I'd really like to have the 21's, just not as practical. Mine will be a daily commuter, rain or shine... here in Oregon, emphasis on rain.
Well if you're getting the performance package (and thus the 21s) anyway, I would give the tires a chance before you blow a bunch of money on the 19s. They might surprise you. I've been running max performance tires on my Audi TT for about 8 years now and they do just fine in the rain as long as I don't thrash it around. The only thing that I won't drive it in is cold/icy/snowy weather.
Anyway, I'll be doing the same (DD in Oregon, live on a hill, etc) and this ^^^ is my plan.
- - - Updated - - -
Unless you really need studded tires like cottonwood, you should get something else. Studs are bad for people and roads. People get silicosis and road wear quickly.
I purchased the Nokian Hakka R studdless variety outside of Tesla.
^^^ This!