If you want coverage, the Virgin is for you.
Virgin offers phones with Analog and 800 and 1900
CDMA, you should have a signal anywhere in the U.S. unless roaming is blocked. Check Sprint.com for coverage and Virgin for rates and roaming.
If you use T-Mo you will be on the 1900
GSM only.
GSM is in major cities and highways. Probably will suffice unless you travel into rural areas.
I would go to Tmobile.com and Virgin.com to get those rates. Whoever is cheaper is probably the best. Watch out for when minutes expire.