While your speed on AT&T HSPA+ network is on the high end of speeds. it is still below what most people who are on Verizon LTE network are getting.
Verizon has what I would call a 4G network. AT&T just starting to role theirs out (LTE)
But like you even pointed out it is around here. You have a rare very fast AT&T connections and apparently slow Verizon LTE. One big thing I have noticed about LTE is that the ping times are broadband level (50 or lower) compared to the HSPA+ that are normally around 100ms.