These days, all of the wireless carriers offer acceptable coverage. Obviously some (Sprint) have limitations like not being able to use data or text while on a phone call. This is because their CDMA network (older technology) does not support this as all the other carriers that are now 100% LTE (Long Term Evolution) would.
That being said, I am often asked which network I am personally with and who I would recommend. Domestically, Verizon and T-Mobile would both be great choices. Verizon because of their bullet proof reliability and coverage in the sticks. T-Mobile's perks are fastest data speeds, no fees or taxes, and in many cases, FREE Netflix.
For those who travel overseas regularly, T-Mobile is the only intelligent choice. With all other carriers, you must notify your carrier and usually select a "bolt-on" roaming plan that "reduces" the roaming costs from obscene to expensive. In some cases, if you don't add one of these packages, your phone may not work at all. This is where T-Mobile is the best. All of their Unlimited plans included FREE Global Texting and Data in over 140 countries. Voice calls are usually $0.20 per minute in these countries.
I just had a client with both a Verizon and T-Mobile line ask me which he should use on a trip to South Korea next month. Again, No Brainer as you can see below. With Verizon, he would pay $1.79 per minute and $0.50 per text. With T-Mobile, voice calls are $0.20 and all texting and data is totally FREE. Duh!
Joel Saltzman has over twenty years of wireless industry experience. He is currently CEO and Chief Wireless Analyst for Dr Wireless.