The GXP is way overpriced. The G8 def has high miles. With those miles, I would assume much of that is highway which is not as bad. I would see if you can negotiate with the dealer on each and see how low you can get them and then decide. I would be leery of financing the G8 though. While it should have plenty of life left, you could be stuck making payments and having a decent size repair pop up.
I would also be interested in seeing what the finance rates are for each. I bet that smaller dealer is likely to have pretty high interest rates. In the end, the difference in interest rates can make a significant difference in the final price you end up paying over time for it.
