It really depends on what part of Maine you live in and frequent. USC has the best coverage of the state, with AT&T a far second, third and even worse Verizon, a very close fourth with T-Mobile, and Sprint pulling in the rear only covering the I-95 corridor up through Bangor.
Unfortunately, USC is a CDMA carrier, which means going CDMA MVNO with roaming agreements with them if you need their coverage specifically. Those roaming agreements, however, do not include data. Ting is a Sprint first CDMA roamer with USC coverage, Selectel is Verizon first with USC roaming agreements and no Verizon 4G LTE handset activation (yet - though it's supposedly coming soon). Unfortunately, this isn't like Wisconsin where the non-USC CDMA networks also have good native coverage in most places and you just fudge the better total coverage with USC roaming in the outliers.
This brings us around to the GSM end, Ting again gets brought up as they have off-network roaming agreements with Verizon's old Unicel GSM network in the area to expand coverage beyond T-Mobile native, and though that coverage does tag more of the state than a no-roaming, AT&T exclusive MVNO, you run into the same data roaming restrictions, the T-Mobile first network coverage and lack of AT&T roaming. That brings us to Consumer Cellular as a better overall option, but once again, you're dealing with data coverage restrictions when you roam off AT&T's native network. That said, of all the GSM options, Consumer Cellular will give you a far bigger data footprint and a slightly bigger voice footprint than Ting GSM and nearly the same voice footprint as US Cellular between all their roaming agreements due to the inclusion of roaming on T-Mobile and the older, Verizon owned Unicel GSM network out in the fringier parts. It all comes back to how important data roaming is and where exactly you're located.
Have some relevant coverage maps:
https://www.consumercellular.com/Maphttps://www.selectelwireless.com/wp-content/themes/neighborhood/my_images/Prepaid_Coverage.gifhttp://ting.com/coverageKeep in mind they're provider network maps, so they're
always overly optimistic on real-world coverage.
If the pricing structure works and voice coverage is more important, your best bet overall coverage wise to reduce costs is going to be Consumer Cellular, but you're going to deal with the additional cost of new handset investment... but that's going to be true for
any switch away from USC to save money, CDMA or not. Again though, it's dependent on whether their pricing structure works for your average usage profile. They are one of the more expensive MVNOs out there due to the roaming agreements and AT&T first coverage, but they can still be worth it if your collective overall usage isn't too high.
If data coverage is the most important, and voice coverage is nearly equal but secondary, you know what game is in town and you're already playing ball with them.
tl;dr: It all comes down to the coverage maps and ensuring you have native network coverage for your primary areas. The four MVNOs in Maine I'd recommend without knowing a ZIP code, in this order, are going to be: Consumer Cellular, Selectel, Ting GSM, and lastly Ting CDMA. All have roaming agreements, and all have
similar voice roaming footprints in the state with diminishing native network and data coverage. None of them can substitute for US Cellular if US Cellular is
absolutely needed as your primary carrier.
You'll note, the native network coverage with those four options goes AT&T, Verizon, T-Mobile and Sprint - the same pecking order as first mentioned on general native network coverage without roaming. Selectel and Ting CDMA both voice roam onto USC. Consumer Cellular and Ting GSM both roam onto Verizon's Unicel GSM, but only Consumer Cellular is AT&T native and inclusive with T-Mo and Unicel roaming. All these providers are likely going to want non-roaming native network coverage for your billing address.
I'm also not sure you could get away with any non-roaming MVNOs, but if you could, your best and most realistic options will only be an AT&T one like Airvoice, H2O Wireless or Puretalk USA, as AT&T is the second biggest native network in the state.
Hope this helps give you a realistic idea of your actual options. Any other questions, just ask.
