Its tough to say man. Service on any provider is dependant on your area. I get fantastic Sprint reception and moderate speed here, but people a state or two away could get horrifyingly frequent dropped calls and speed slower than average 3G. Its something you end up having to test for yourself, or ask people you know. All carriers have bad cities for service.
Verizon is pricey, but it is true about their LTE speed, it is fast, and it is available in a LOT of places now, and expanding quickly. The data costs will destroy you however unless you take advantage of a deal they have going through the 30th of this month that will give you 2 times the data you pay for, at the same cost. Buy a 2Gigabyte plan, and they will make your data limit 4GB instead.
Sprint on the other hand is just unlimited, so you dont even have to think about it, and they start their LTE rollout next year. But I wouldnt expect their speeds to match Verizons LTE, and it could be a long time before Sprints LTE makes it to your area, and any phone you buy now wont support their LTE either, so youll be on WiMax speed for 2 years.
Its a really tough call. If you like the phone you have, and the speeds in your area are great, and the reception is good, stay with Sprint and keep the phone you have. Worst case scenario, you go 18 months with a fantastic phone, with unlimited data and great call quality and speed. Worst case scenario, you test the grass on Verizon side, only to find out, in your area Verizon actually sucks.