Just for the record 4G is no longer CDMA vs GSM, it's now WiMax vs LTE.
Sprint is going WiMax and both AT&T and Verizon are going LTE. And I dunno where that 2 year "exclusive" 4G thing is coming from cause Verizon will have their LTE 4G networks up in the fall, and AT&T will have it 2012.