As an engineer with some background in properties of metals, the nickel in stainless won't be affected by grilling temps. That said, there are many grades of stainless and some stainless grades can rust. Nothing like plain steel though.
I'd go for the stainless grills.
Dr. Mark (STL)
Ph.D. (honorary) Bovine $hitology
A thin line separates paranoia from an acute understanding of reality.