When it comes to 4G, there are lots of claims floating around. Sprint claims to have the most powerful, T-Mobile says it has the biggest, and Verizon promises to have the fastest. But some of these claims need to come with footnotes.
That is especially true in the case of Verizon. If you're in a spotty 4G coverage area, you might have to switch back and forth between 3G and 4G. It doesn't sound like a big deal. After all, every 3G phone out there already knows how to deal with a situation like that. It automatically converts between a less powerful signal and a more powerful signal. It's seamless to the end user.
Not with Verizon 4G, though. If that 4G connection is lost, even for a second, the phone will switch to 3G mode. But to get back to 4G, you'll have to wait as much as two minutes. That's right; if you're in a car and you pass over a dead zone or whatever for just a couple seconds, you'll need to wait another two minutes for your 4G connection to "refresh."
This is a phenomenon unique to Verizon, as AT&T's and Sprint's respective 4G networks don't have anything similar.
Verizon's 4G network is based on a technology called LTE ("Long Term Evolution") which is different than Sprint or T-Mobile. Thus, Verizon is the only one who can troubleshoot it.
The mobile carrier says it is looking for ways to fix the little glitch, but right now it's not a simple problem to solve. It isn't a deal breaker, because as long as you're always in a 4G zone, you won't have to worry about it. But in places where reception is spotty to begin with, this just adds to the headache.