I will go against the majority, and say the SS do indeed last longer, especially with high heat guys.
While I agree there doesn't "appear" to be much logic to it, as they posess the same poppets and o-rings (soft goods) as the brass, so my theory is thermal expansion and just overall durability of the 303 stainless. All things being equal SS won't expand as much as brass and won't wear as fast, this might be the difference on a marginal seal giving way in a brass housing or lasting a few months more in a SS housing.
In general SS cost 2X as much as brass if not more, so you have to balance the purchase of a Female, but the Males are a no brainer, nicked o-rings are a pita.