I have the i777 and my wife has the SR. When we're in NYC, her data speed is a ton faster than mine (because of LTE), so LTE in NYC works just fine. Honestly, through daily use, both phones are great. Many people around here will tell you to stick with the i777 but I'm not going to sway you one way or another. I have access to both devices and they're both really good. Although, I find the ICS roms on this device are more stable than the SR, IMO.
Friend of mine has the Skyrocket. We were in NYC yesterday for the auto show so he had those LTE speeds unleashed and they were pretty damn impressive. They were totally destroying my HSPA+ speeds. I've played around with his phone on other occasions and it really isn't that bad at all.
Both are really good phones.