I wouldn't waste money a full system, just gut the cat in your stock headers and run whatever slip on you want and the money you save can go into fuel management, tune etc. Full system is kind of a waste on these bikes unless you are racing and really after shaving every extra ounce off the bike. Stainless will weight about the same as stock, and ti will knock off a pound or two depending on which company you are going with. So I'm not sure the extra 1000+ dollars is worth maybe 1-2 hp and maybe a few pounds.
And not sure what you mean exactly by Moto gp style exhaust throw out a few examples that you are looking at please.