Walk around weight is not relevant. No matter how many times it's posted, it's still not relevant. Cage weight is relevant. All that 228 means is that Bisping is getting too big right now and will have to work even harder than normal to get down to 185.
No. They have to weigh at most 185 about 36 hours before the actual fight. They can weigh whatever in the cage. GSP will fight right around 195-197, and Bisping will fight right around 200-205. At most I expect a ten pound difference.
The reach is almost identical, the weight will be 5-10lbs, and Bisping will have a 2" height advantage. Michael is certainly bigger, but he will not outweigh GSP by more than 10lbs come fight night.