Looks like Ontario is a little closer. Reno's more direct (a straight shot down 395).
I may be biased due to my living Northern Cal, but I think the view of the mountains driving down from Reno is better.
Any properly maintained modern car shouldn't have radiator problems on 395 (it's not really steep anywhere that I can recall). Going up to the Portal or Horseshoe Meadows will put some stress on cars (think I finished off my rear brakes last year
).
