Onstar uses gps for location and cell for data, they say they use various, some say att, but the antenna and output are better than a cell phone.I guess the Onstar unit has a built-in wifi in the vehicle? Sounds like a heckuva deal!
If so then its back to how good is the ATT coverage cell wise. Verizon was #1 for years, I've had best luck on the road for years with ATT traveling the entire western US but... one day I'll tell a funny story on myself trying to troubleshot a new phone connection in a bad spot on the top of a hill next to the ranch exit on south side of I80 somewhere between Salt Lake and Laramie...in the freezing cold winter wind blowing 30 kts...
Yes, ATT had literally hundreds of miles of dead zone on the interstate in the Red Desert with no cell service back then...
"Baaaaaaa...who's your daaaaddy!"
I'm sure its gotten better since...
And new phones are much better radio signals wise. Trust but verify those coverage maps...
I'm interested to hear how the T-mobile deal with Starkink is working out...so far text only but that saves paying for a garmin device to text updates to family from the back country.
My cellphone uses Verizon 5g , in Maine I had no cell phone unless I turned on the hotspot., recently in nh at a notorious dead area , again the hitspot worked.
So I'd say so far for me it's great, im heading to Wisconsin next week and will report back .
It may not be actually satellite, but seems better than regular cell phone, also satellite is $400 for the equipment and $50 a month for service, whereas onstar is $24 a month and no antenna purchase.
They'll give you a free trial , if it's not good enough no loss