I just switched from AT&T to VZW and I don't live in a spectrum-squished space like you folks in NYC.HSPA+ is a gimmick. AT&T's 3g network is theoretically faster than verizon's 3g + is faster in speed tests, But is slower in most real life tests compared to Verizon. It has slower pings + the service is horrible on AT&T (Here in NYC at least).
AT&T's HSPA (not HSPA+) network here regularly sees throughput between 1mbps-2mpbs. From my two days on Verizon, I have yet to see anything over 400kbps.
Web surfing seems to go a little faster on Verizon. I guess that's attributed to the lower latency.
However, anything that involves moving a decent amount of data (i.e. downloading apps or music from the App/iTunes Stores) are ridiculously slow on Verizon here. Words with Friends took almost 2 full minutes to download over VZW 3G last night. Working with Verizon's tech support, they told me that 1.2mpbs was about the fastest their 3G network goes, and that's if nobody is using it, and the speeds I was seeing (200-400kbps) were about average.
I never had a major problem with AT&T's coverage here. I'd rate it at 90%. Verizon seems like 95%. Not a huge jump for me, and definitely not a situation like you folks that lose AT&T completely all the time, like in NYC. I've got to figure out if the extra 5% coverage I get from VZW is going to be worth dealing with their slow 3G network speeds. At least I get 13 more days to see if it's worth the switch, for me.