If you all live back East having wrap on the stock steel header will certainly show major corrosion internally because of all that damn moisture. Here in the hot SW we don't have these issues. SS will corrode also just not as quickly. If the SS is thin like what Brock puts out or at least did back in the day with the Hindle/Brock systems, it will suffer from corrosion as well. Seen it first hand on 2 bikes out here and they did not have wrap. Pin holes after the bend of the primaries to the collecors. Moisture settling in that area?
If you spent the big bucks on Titanium, it is suggested not to wrap it as well according to the expert mettallurgists out there. Even ceramic coatings on titanium I hear is not a good idea but I really do not know for sure. Never tried it but thought about the coating.
Now on ceramic coating, I have had it done on many projects over the years from HTC, Jet-Hot and a local company Synergy Coatings. All of them looked good and held up ok. But you still cannot touch a header or turbo housing with your bare hands. I cannot say that it is much different than no coating at all IMHO. I started spending the big bucks and now use Swaintech. This stuff is the real deal but it is still not advisable to touch it too...lol but you do notice a difference. I have also used the wrap and it is the only product that really keeps the heat down substantially and you can touch it for short amount of time. Just a little PITA get.
Performance gains? So hard to measure on a bike but on a car it might show up as an advantage.