Xfinity/Comcast deal is with Verizon, not Sprint. The deal to allow Xfinity Mobile to use Verizon happened years ago. Doesn't change much or any reasoning, but VeriOn is a lot better in terms of service area [and strength] vs Sprint.
Verizon has poor service in many places, eg Hawaii or when roaming up near the Canadian border. They still haven't figured out how to support international roaming reliably, half my family was w/o service for our few hours in Canada. Service in SoCal seems to be one of their last strongholds, but even then voice calls sound like a robot.
Took multiple support calls and 2 hours of our time to get their phones to roam in Canada, whereas the rest of us were up and running when we landed. Nevermind, once we got their phones working, outbound calls still didn't work on iPhone or Android, it'd ring outbound and the other person would get the call, but the call would collapse on answering it.
Comcast using Verizon doesn't have that problem in Canada at least the two times so far I've been there with their phones. Worked instantly and the prices are rock solid. Hate still having Att as my main provider when going anywhere outside America.
With the highest priced international sprint service i had terrible connection in Paris several months ago. I would go 30 mins to an hour with no connection frequently.
At home (Boston Ma) sprint is good enough to online game and stream at the same time. I lost my comcast connection for several hours recently, and tethering to my phone resulted in less latency...
Edit: This is on Sprint's unlimited plan (around $50 a month for 1 line, $25 per line for 4 lines)
If RCN is available near you (I'm in Watertown), I highly recommend them. I was used to very frequent Comcast outages but haven't had a single issue with RCN after subscribing for almost two years.
