IP4: Sprint vs AT&T data speedsin WPB Fla

My wife just got a company iPhone 4s, Sprint... I have a '4' AT&T ... Just out of AT&T contract & thinking bout going ta sprint for 'unlimited' .. Downloaded two speed test apps ... Tested both side-by-side at three different locals far apart in town (miles). Blew my mind! Average 3G Data times: AT&T : 2.5 - 3.5 dl x .9 - 1.5ish ul ... Sprint: .01 - .35 dl x .01 - .17 ul .... I don't drink AT&T Coolade, but man that's a HUGE difference ... I don't know if it's the Amount of people on Sprint, or, garbage hardware/software - or a combo ... Don't know if I can't believe just how much better it will Really get with TLE towers (& TLE phone) etc, or, will the seemingly Huge amount of people on that network (sprint + Virgin etc) will still 'bottle neck' even it's New coming towers ??? Any ideas??