We have used Garmins for 12 years. The newer Nuvi's have more features but tend to have a high failure rate for me, mostly quit communicating with the computer.
I keep a Nuvi 550 as a back up. Cell phones are ok when they work but as noted Verizon coverage in the TX hill country is poor.
We have to build our own routes on the computer because we avoid interstates. Sometimes US hwys are tricky through small towns as the paper maps don't have the detail.
For the older Garmin's there are work arounds for lack of memory.