I'd take the G35 over the 350Z. However, you do see less 350Z's on the road whereas with the G35C, they are everywhere.

Up here, resale values seem to tell a lot about the popularity.
I'm seeing used 350Z's in the mid 30s (20k KM) and similar G35C's selling for high 30s. So a 5k price difference on the used market.