I paid a lot to upgrade from a 4s for speed. I'm on 4g now getting worse speeds than I was getting on my 4s in the dog park. even at 6 that's not good. less than double speed is the the ten fold increase I expected, the 15 fold increase Verizon gets in the same area.
Speed tests don't show the real story anyway.
The point is are you able to access data and perform functions well?
When I had my AT&T 4S I compared VZW LTE devices and with side by side comparisons there wasn't much difference between the two. Ok VZW LTE loaded up NY Times full desk top version a second or 2 faster. Nothing to write home about. Although speedtest app showed VZW to be faster you can't see a difference.
Now I have apples to apples to compare; AT&T iPhone 5 versus VZW iPhone 5. Side by side comparison you can't tell the difference. Using the speedtest app sometimes AT&T is faster and sometimes VZW is faster. Both carriers go in and out of LTE to AT&T '4G' or VZW 3G. When this happened the you can tell the difference because AT&T '4G' noticebly performs better than VZW '3G'. Otherwise both LTE networks you can't notice a difference with side by side comparison.
People like to get into pissing contests about their speed test results but they don't really show the real story in real life uses.
What's important is does your iPhone 5 perform when needed?
Stop doing speed tests and enjoy your iPhone 5. Now if data sucks that you can't use your iPhone 5 then a different story, find a carrier that works in your area.
(note the above is dependent on the area of course. My experience is in the Philadelphia area/South Jersey)