The miles are relatively low on your truck (the one you're looking at). It's hard to say on any vehicle if it'll give you trouble or not. You could call GM service and see if it's had all the warranty and recall work done. It's all personal choice what ya like and how much power you think you need.
I've driven an 06 that was almost a carbon copy of mine, same basic options. The 06 I drove didn't feel like a dog (on flat ground). I guess mine did have a little more power, but seemed like more low-end power for like pulling away from stop signs. These vehicles weren't race cars, but between the two, yeah, I'd go with the 07. My 07 is very good for daily driving. Do you need extra power for like trailer towing? I'd look at the overall vehicle, the options, condition and decide if it meets your needs. Give it a good test drive. If you think it fits your needs and looks like it'll work, give it a go. Yeah if you live in a hilly region ..or even the mountains, you might want the extra V8 power. I've had Jeep Grand Cherokees with I-6's and V8's and yeah the V8 moves the vehicles around nice, makes everything easier. But thirstier too.
But from a reliability standpoint, hard to say. You'd think any major problems would have surfaced and been resolved by now.