i have a 550i and was debating driving it this winter. i currently have all-season, and i know they are not that great in snow.
how much of a difference will snow tires make?

Idk how much better snow tires will work than all seasons, I do know studded tires kick ass! They'll get u thru a foot.

Install 4 good snow tires and you'll be amazed at what the car can do... :cool:

give me scenarios ^_^

+1 On good snow tires. Totally worth everything you pay for them. I had a set of Blizzaks.

Ok, scenario: First snow in Detroit. I back out of my garage in regular tires and I get stuck when my back tires are 3 inches in. I make it into work Tokyo-drift style, going 20 mph. Later that night, again going slow, I bump into a snowbank with ABS on for the last 30 feet and decided I'd had enough. After snow tires, it's like driving on a wet road with some limitations. If I never see snow again, it'll be too soon.

It really just depends on the type of winters you get...
Last year i got away running all season p6 pirellis, not this year though...I had to get Bridgestone Blizzaks LM-60s, they really do make a huge difference.

When my inclined driveway is covered in sleet, snow or ice, my RWD E60 on Blizzaks has no problem making it up into the garage. My wife and daughter have FWD on all season - they have a more interested trek up the driveway. Any questions?

Consider the insurance deductible for a winter fender bender or encounter with a curb/railing. That would be the financial justification for a winter wheel/tire set.

(Disclaimer: I have to have winter tires, since I use summer tires the rest of the year.)

A good set of Blizzaks on 550 will make you wonder why people would buy an xi. Its that good

Unless you're an XI owner with a good set of Blizzaks or equivalent. :) Snow Tires and AWD equals a TANK. I love it so!
Not a winter XI example, but a good one. I was picking pumpkings and apples at a popular local apple farm. It rained the day before and with all of the cars in and out the parking area started turning into mud. They had kids working there pushing cars through the mud to get them out. Needless to say I drove through without issue :cool: The kids were happy not to push me, the drivers I'm sure had a tiny bit of envy at that moment.

With a RWD car :) snow tires will help stop the back end from spinning on when you give it too much gas in the winter, and improve your stoping distance big time. I would advise everyone to get a set IMO.

I never used to use snow tires until I bought my first bmw, and the only reason I decided to try was becasue I had bought aftermarket wheels and had an extra set of rims laying around. After having snow tires I can say that I don't think I will ever go without snow tires anymore. The difference is huge, you notice it most in stopping distance. Another scenario, is they make enough of a difference that in some places in Canada it is the law to have to have snow tires on your vehicle in the winter.