The baffles on my 1955 Cessna 180 are aluminum and have lasted pretty well. The original ones went over 3,000 hours and an engine overhaul before being replaced along with the engine. They are still completely serviceable.
I'd avoid stainless steel for two reasons. First is weight, of course, but second is that if there's going to be any chafing, you'd like the baffles to be the sacrificial part and not the engine.
Make that three reasons - you don't want to get slashed while you're working in the engine bay.
Dave