iPad Mini LTE question

So I recognize that the iPad Mini with LTE isn't available just yet, but I was told that I could get one for Christmas (thanks Mom and Dad!) and I had a question about the carrier options. I understand that due to the nature of their LTE networks, the LTE in the iPad Mini for a specific US carrier will not work on other carriers' LTE networks.

That's all well and good, but I was wondering about the specific advantages or disadvantages that a certain carrier's model may have over the others. For example, I have Verizon LTE on my Galaxy Nexus, and was probably going to tell my dad to pick up the Verizon model for me, but does the Verizon model have CDMA to fall back on when I'm not in an LTE area? Furthermore, if I travel, does the Verizon model have a GSM radio that I would be able to use overseas? For that matter, does the AT&T model work on networks overseas? And what about in Canada, is there a US model that can make use of Canadian LTE?

I was looking at the tech specs on Apple's iPad page, but to be honest I could never keep all of the acronyms and frequencies straight or remember who used what and what worked where. Any insight would be greatly appreciated! Thanks!