Snow tires - Blizzak or Pirelli Scorpion?

I'm looking at the Blizzak DM-Z3 265/60-18 and Pirelli Scorpion Ice & Snow, either 255/55-18 or 255/60-18. These will be mounted on the stock 18x7 wheels and only used when it snows. I will swap back to my Pirelli Scorpion Zero 285/55-18s, also on stock wheels, when the roads are cleared. The tire rack reviews rate the Pirelli just slightly higher than the Blizzak, but the number of reviews and mileage is far less. Should I give the Pirellis a shot, or go with the tried and true Blizzaks? The smaller Pirelli should be about the same height as the original Dueler, while the larger Pirelli and Blizzak will be about an inch taller. Is tire diameter a significant factor in snow? If so, which is better? Any suggestions on tire pressures for use in snow?

My wife's VX is just about to get the Blizzaks put back on for the 3rd winter. This is a very good snow tire and I would highly recommend them. This will be the last season for them.

Tru:D