As someone with Sprint and a 4S, go with Verizon. The first issue is coverage in your area. I live in VA, and at my apartment, the coverage is next to zero. It improves everywhere else.
The other issue is going to be the slow data rates. When I upgraded, I was lured by the promise of unlimited data rates, but in all honesty, I looked at my usage, and it was like a GB. So the cap Verizon places on you won't really affect you unless you're doing crazy surfing, etc.
Also, the battery life is supposedly better with Verizon for some odd reason.
Don't let the $69 fool you.