OK, I'm ready to make the jump to an iPhone 5 (leaving T-Mobile US after decade+ with them) and am choosing between iPhone 5 with Verizon v. AT&T. You can help.

First, I H.A.T.E. HATE HATE HATE AT&T. They are the reason I long ago went from them to T-Mobile (then Voicestream). I've sworn to forever not patronize AT&T. That said....

Second, I generally understand that Verizon's iPhone 5 and AT&T's iPhone 5 both function internationally although they may not be LTE when traveling internationally. They are, for all intents and purposes (in this thread), both world phones just with caveats re: data speed when traveling abroad. OK. So, I suffer from data speed loss while abroad. No issue and frankly, I'd probably not roam on an international mobile network for data and instead use Wi-Fi for data.

Third, it looks to me, at least, that Verizon's LTE coverage is far wider than AT&T's in the United States. I'd prefer the widest LTE coverage, so that tilts toward Verizon.

The big question for me on the Verizon v. AT&T front is this idea that, with a Verizon iPhone 5, you can not be on a call and surf the web at the same time. This concerns me as I'd like to use the iPhone as a Wi-Fi hotspot as well.

So, if I'm on a call or receive a call with a Verizon iPhone 5 my data connection drops out. Right?
Is this really a concern?
Do Verizon iPhone users ever really encounter this type of problem or is it a big issue?