I have Sato's on my 919 and Yoshi's on my RC51 now. I had Yoshi's on my 919 and Sato's Banzais on my RC51 in the past. In my opinion Satos are the best sounding exhaust period, much to loud on the RC51. The Yoshi's are some of the best made there is, you will sell your bike before the Yoshi's give up. There are virtually no replacement parts for Sato's. On the other hand Yoshi parts are just a phone call away. A stainless exhaust will last considerable longer then a light weight titanium exhaust for the street. The Sato's on the 919's are stainless except for the sleeve and for some the core.
With the Yen where it is. A hand my titanium exhaust will cost you almost as much as you bike is worth.