I have 3-Spypoint 4G and 2-Spartan GoCams in use right now. As of now, the Spartan is the best between the 2 right now.
We have had the spypoint for a few years on the Verizon Network. We had issues in small valleys with getting signal. The picture quality is ok. We are using 12v external batteries with them as well.
I found the Spartan GoCams last year. These I have on the US Cellular network. (the also are on Verizon, Spring, and AT&T). I have had zero connection issues in low lying areas. Picture quality is good. Pictures are almost instantly available to view via email, text, or only website. Big thing with the Spartan is battery life. If you're going to just use AA batteries, you'll be switching out every couple weeks depending on how many pics they're taking. So an external 6V battery is a must IMO. I bought the biggest 6V i could find and made up an external battery. If you're going this route, you need to use rechargeable AA in the camera. If you don't, the cam will drain the AA first and not the external. There's a video on youtube explaining this and seems to hold true so far for me.