Snow Tires or Not?
 

I'm using 20s for daily drive and have my 19's for mountain ski trips.

Not sure what I should do for tires.

Options
1) Stick with Michelin Touring HP's (all season) and use cables when snow's on the ground
2) Sell the Michelins and buy focused snow tires like the Pirelli Scorpion Ice and Snow RFT @ ~$250 each (might not be so great when it's dry?)
3) Sell the Michelins and buy performance winter/snow tire like the Bridgestone Blizzak LM-25 RFT at ~$340 each

Thoughts?

Anyone in southern CA interested in buying my 19" 255/50/19 OEM Michelins w/ about 150 miles on them?

I run the Pirelli scorpion snow and ice roughly from november through march, they are excellent on snow and when dry, no complaints at all
I used to have the blizzaks on the previous bimmer but I can't tell the difference in handling between the blizzaks or the scorpions so I don't see the need to spend the extra $

1. snow tires are best for snow/ice but also for lower temperatures (below 40° F or so)
2. if you use chains on summer tires, you need to use them on all FOUR wheels (which can be a pain in the a.. if you have to mount/remove them all the time, top speed with snow chains shouldn't exceed 32 mph for safety and reliability reasons)
3. for ice and snow, choose the lowest speed index available in the manufacturer recommended size. BMW sells the 19'' wheels with 255s on them but they have a V speed index and this is usually useless in the US because you never get to drive up to 149 mph in winter time in the US. Get H or even T rated winter tires, the only problem is to find the right size and the right LOAD INDEX (very important too) for your car.
You would be surprised what even the jump from V to H speed index on winter tires can do, the difference in handling/braking improves substantially.

I live in Bavaria and I'm travelling to Austria very often, so I have my share of experience. ;)

Also don't forget one last thing: the limit is the...ground clearance. If the snow is much higher than your ground clearance, the best winter tires/chains can't help much, stay away from it. I had to grab a shovel several times to help to get some people out of the snow and they were driving much better Off-Roaders for winter time.