I'm going through the same decision right now. I played with both today, and I am still undecided. I'm a current Verizon customer, and I would have to break my contract to get into the 8700c.
Overall, I think I prefer the 8700c, but I'm not sure its worth switching over to Cingular. It's more slim than the 7130e, with the bigger screen, plus a full QWERTY keyboard - which I think I really prefer. The advantages of the 7130 are the faster EVDO network, the ability to hook up to my laptop for a modem, and I would not need to pay to get out of my verizon contract.
I'm still up in the air. I wish I had more concrete news that the 8700 was coming to Verizon in the next month or two, then I would just get the 7130 in the time being. However, I fear Verizon won't get the 8700 until next summer.