I read also, that the SII was not 4G. I'm not sure if anyone can confirm this, but that would be a deal breaker for me. My next phone will be 4G for sure.
As long as the GPS works good, and it's a 4G phone, I think I'm going to get the Samsung. The reception on the Fascinate right now still works ok, I just don't get as many bars as I did on my D1. I don't drop calls or anything like that.