Anyone use Xfinity Wireless, Mint Mobile or Google Fi?

Over the past 20 years, I've had cellular service with all the major providers:  Sprint, T-Mobile, AT&T, and for the past 6 years, Verizon.  I like Verizon's coverage, but I don't like the monthly cost.  Now that our cell phones are paid off, I'm looking into potentially moving to a new provider.  I'm considering going to Xfinity Wireless, Mint Mobile, or Google Fi.  Here are my pros/cons for each:

Xfinity Mobile:  I like that it uses Verizon's network, and the pricing seems pretty good, too.  It's $45 per month per line for unlimited data, or $12 per gigabyte used.  Since my family hasn't topped 5 GB a month in years, the $12 per Gig plan would work for us, and we'd be saving a lot, while remaining on Verizon's network.  I don't like that it's through Comcast, though.

Mint Mobile:  Mint offers various packages from 3GB to 12GB per month in either 3 month, 6 month or 12 month plans.  It seems to be the lowest price among the 3 I listed, but I do not know much about this company, nor do I know anyone who uses it.  I don't like that Mint works off the T-Mobile network, as my brother has TMobile and tends to have issues with the network.

Google Fi:  Google Fi would be $35 for talk/text, plus $10 per GB used.  Based on my family's data usage, this would probably be the most expensive of the 3 I listed.  I know a few people using Google FI who like it, but I don't like that it bounces between T-Mobile/Sprint/US Cellular's networks for data.

In summary, I'm very skeptical to move from Verizon's network, as I fear that I may be moving to a slower network, but I do want to get away from the higher costs and saving where I can would be nice (damn daycare bills suck).  

So...anyone here on any of the networks I listed?  Has anyone ever switched from a "major" carrier to one of the ones I listed (or other)?  If so, what have you noticed in your service since you switched?