I was curious about this. I'm running a Galaxy Nexus (clean Google phone from the Play store and Jelly Bean) on T-Mobile right now, but the phone isn't LTE, so I'm stuck on the HSPA+ network... which kind of sucks. Looking at speed tests and heat maps from PC World, etc. it seems that AT&T 's 4G and Verizon's 4G were pretty close in my area (Dallas/Fort Worth).
Has the mass release of the i5 jammed the networks up? I'm going to switch to one of the two and the Note 2 when it releases, and barring any new studies being published, am just curious what the networks are like POST-i5 release.