I am very happy with my Moto G on PTEL. I don't know why PTEL isn't more popular. The coverage as far as I know is the same as t-mobile. Not the best, but it works for my location.
Potentially because T-Mobile direct offers the same plan for $5 cheaper than PTEL does. (TMO Simple Starter 2GB at $45/month vs PTEL 2GB 'Unlimited' for $50/month).
T-Mobile also has lots of advertising and lots of physical stores, which probably helps a bit.
Glancing at them real quick, they're a T-Mobile MVNO and their mid-range unlimited plan is $50/month with 2GB of high-speed data. Straight Talk, which is usually on T-Mobile but depending on device and region also uses the other three major carriers, is $45 for an unlimited plan with 3GB of high-speed data. And MetroPCS, owned by T-Mobile, is also $50/month for a mid-range plan, but with 3GB of high-speed data.
Unless it has better roaming priority, I don't see what it brings to the table (maybe pay-as-you-go is a different story, though, if that's what you're interested in).