I am dithering between the new iPad models: AT&T vs. Verizon. Which if either would be better for international use? Don't most countries use GSM, which AT&T uses? In other words if I wanted to use the new iPad in other countries on occasion (Mexico and Europe) does it matter which model (AT&T or Verizon) I get in the USA? For sure their 3G modes are quite different, right (GSM vs. CDMA); is their 4G different also?