It depends what your priorities are. The Blizzaks can be very good on ice, due to their very soft tread compound. However, that also makes them a little 'loose' in the handling, and they wear fast. I have read that the Blizzaks' sipes (the cuts in the tread blocks, which are critical to winter performance) go only halfway through the tread blocks. They could not go deeper because of the soft rubber. The soft rubber also only goes halfway down (5 to 6/32"). So when you wear them to halfway down, they lose their ice-gripping power, and you are supposed to then leave them on during the summer and continue to use them as basic all-season tires (Bridgestone actually recommends this). Then you buy a new set of Blizzaks the following winter. Sounds like a great money-making scheme for Bridgestone - running Blizzaks all year 'round!
I chose Pilot Alpin PS2 tires because I drive mostly on the highway and Blizzaks (or, Michellin X-ice, etc.) would burn away in no time. Pilot Alpins are a performance winter tire, not a severe condition winter tire like the Blizzaks. Performance winter tires handle better and stand up to high speeds and/or warm temperatures better. They often come rated in H or V speed rating, which severe condition tires do not (usually S rated). European performance sedans are often equipped with performance (aka European) winter tires. You need to determine which type is a better match to your driving habits. Better traction on sheer ice doesn't necessarily mean one tire is better than another.
Whatever you choose, I'd recommend considering going to 215/55R17 instead of 235/50R17. Narrower is better in winter (less floating on snow) plus they are usually cheaper. The 215/55R17 is a nearly perfect diameter match to the 235/50R17, and they fit fine on the 7.5" OEM rims.