I can only speak for the two networks I have personally had experience with.
Eliminate customer service.

AT&T is horrible in the tri-state area. I think the frequency of dropped calls and lack of coverage for the price you pay is unacceptable. Outside of NYC service is great but everyone who doesn't believe me and stays a week in NY says it really sucks!

Sprint works. Data may not be the fastest (don't have benchmark against other carriers) but never a problem and if you are dropped or dead zone you immediately roam over to Verizon CDMA network (e.g. train tunnel between NY/NJ on Amtrak) plus it doesn't hurt it is the most economical smartphone planes with unlimited data.

You must ask the question what is your usage requirements? Are you tethering via your phone or basic small apps (Dinner reservation, movies, flight checker, GPS)? I ask because people make a big deal of data and multi-tasking (retrieve data while talking on phone) but many times the same folks rarely are doing both.