I am assuming this process will work out to be the same as the current situation with iPhones:
- Backup your iPad using iTunes.
- Plug new iPad into same computer.
- Restore new iPad from old iPad backup.
When this is done with an iPhone, the new iPhone will be configured exactly as the old one - save games, email apps, photos, everything is transfered.
What happens is actually that the backup contains all app data + configuration. The rest is basically a list of stuff that should be synced from your computer to the device (e.g. music, photos, apps).
Yes, the two models are physically different. The radio is different.
As per Apple's website, the radio frequencies aren't the same. The verizon iPad supports Verizon LTE, and as per this post, AT&T 3G. However, the Verizon iPad does not support all LTE frequencies that the AT&T iPad does.
From Apple.com:
Wi-Fi + 4G for AT&T model: 4G LTE (700, 2100 MHz); UMTS/HSPA/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz)
Wi-Fi + 4G for Verizon model: 4G LTE (700 MHz); CDMA EV-DO Rev. A (800, 1900 MHz); UMTS/HSPA/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz)
Notice that there are some differences between the listed frequencies. They're nearly the same, but not quite.
Edit:
To confirm, the difference is a hardware difference, not a software imposed limitation on AT&T LTE. From the Macrumors article:
The Verizon iPad hardware supports only the 700 MHz band for LTE to match the carrier's technology, while the GSM version sold for use on AT&T's network supports both the 700 MHz and 2100 MHz bands as used by that carrier.
If you're looking to travel internationally, go with the AT&T iPad. (I got the Verizon iPad because I wanted the free hotspot feature, which AT&T does not offer for free at this time.)
Best Answer
I've always involved the carrier, but I don't know if you have to involve VZW in the switch.
If you have a shared data plan, then you will certainly want to get them involved to ensure you don't make a stand alone plan when the old SIM hits the new device. I've had no issues with exchanging a device and not had to pay the fee for enrolling the new device since it simply replaced the old one.
If you are on a month to month plan and don't mind re-paying the activation charge, you could simply set up the new device and let the old device's plan expire.
Much depends on if you use the device to set up the account or want to have verizon enter the details into their system as the different types of accounts have different manners of adding the new device to the plan.