Voice Quality on iPhone 5 My setup is iPhone 4 and Bluetooth in my 2012 SUV.

I have a 80 minute highway commute.  I have real trouble hearing the other party at highway speeds around 65 Mph or higher.

If I drop my speed down by 15 Mph, I get much clearer voice quality.  The phone shows me either max bars for connectivity or 4 bars in either case.

This leads me to believe that it is not the Bluetooth, or the quality of the phone itself, but the quality/strength of the signal captured.

This is the only reason I am considering switching phones. The iPhone 5 for AT&amp;T has the 4G LTE network.

Is voice quality better because the 4GLTE is a faster network?  Does the quality of voice issue at high speeds go away for the LTE phones?
LTE is a data network and voice calls still use 2G/3G. I expect that your problem is related to your call being handed off from one cell tower to another. 
The iPhone 5 or an LTE phone in general is not going to solve that problem for you.