good advice..thx TrotterMetro = T-mobile, Boost = Sprint. They are ranked #3 and #4 respectively.
It boils down to their coverage in your area. If you are in a metropolitan area then you should be in decent shape with either as both T-mo and Sprint focus on them. In a rural area it will be more dicey.
If possible I would go with AT&T/Cricket or Verizon/Boom for the coverage offered by them.