** My current iPhone 5 VZW issue update **
I think I will take something back that I said earlier. Of all the things I tried (3 devices, reset the device, reset network settings, SIM swap, etc), I think the SIM swap had SOME impact. Prior to the SIM swap, phone basically never went to LTE unless i forced it and when on LTE, almost never worked reliably. With the SIM swap, a strong LTE signal does in fact work as I would expect it to.
I just did a quick walk test towards the tower and found that my phone did eventually move from 3G to LTE on its own (which I don't see very often). Unfortunately I was in a strong LTE area for a *very long time* before it decided to kick over to LTE, so I think there is something messed in the SW which decides when it's OK to switch. I sat around with -80 dBM and 4 3G bars and it just did not want to move to LTE on its own.
I think I am really down to two main issues with the iPhone 5 VZW, which is crummy signal strength (compared to other iPhone 4/4s and Android LTE devices) and phone just holds on to 3G way too long when it could be using LTE, they may or may not be related problems. In lower signal strength areas, Android phone would be locked still on LTE, the iPhone 5 picks up either 3G or lower strength LTE which becomes unusable, even more so with uploads than downloads.
Summary:
Transition from 3G to LTE when signal strength becomes stronger is not happening reliably and/or fast enough unless you force it by toggling airplane mode. It's almost like the phone wants a perfect 5-bar LTE signal before giving up on 3G.
Lower strength LTE (or perhaps signals in general) are not picked up anywhere near as well on iPhone 5 as other devices, like Galaxy S III
Lower strength signal area makes phone either provide unusable LTE or lock hard on to 3G.