Trying to decide between 2 notebooks...

So I'm looking at two notebooks. There is a pretty significant price difference, but there is also a kicker that makes this a two part question. I'm looking at a MSI GX60 1AC-021US VS. an Ibuypower Valkyrie cz-17 (slighly older version) I'll post the specs for both at the end.

Here is the kicker, the Valkyrie is used and I'd be buying directly from a guy on craigslist.

So in the community's opinion which computer is better for the money, and would you consider buying a computer from a guy on craigslist?


Valkyrie cz-17 $850 from a guy on craigslist:

8 months left on manufacturers warranty. He'll print me off a copy of his newegg invoice so I could send it in if there are issues.
17.3" FHD 1920x1080 (Non-Glare Type) Screen
8 Gigs Ram 1333
Intel Core i7-3630QM 2.4g Processor
Nvidia GeForce GTX 670M/ 3GB GDDR5 Video
750GB 5400rpm HD
Keyboard Backlit
Windows 7 Home
No driver disks/windows disk
Rest is pretty much the same


VS

MSI GX60 1AC-021US $1100 Brand new

Full two year manufacturers warranty
15.6" Full HD LED-Backlit LCD Display (1920 x 1080)
AMD Quad-Core A10-Series 2.3GHz APU
8GB DDR3 SDRAM (4GB x 2) 1600
750GB 7200RPM SATA Hard Drive
AMD Radeon HD 7970M Graphics with 2GB GDDR5
Windows 8
Should come with backup disks


I don't really care about the size difference, I slightly prefer larger, but I'm fine with 15.6. I don't care about processor that much (as long as it can do the trick) although I slightly prefer the i7. I care about video cards: the gtx670m vs 7970m is a huge difference in favor of the MSI. And I care about warranty.

So what do you guys think?