tough to decide between the Yoshimura exhaust and RPG, both sound close to eachother but quality of the video could be changing the tone a bit. I think it'd help even more if we can hear these in person.I really like how the MSX125 RPG exhaust sounds, and I think the video below of it is quite convincing that it may be one of the best sounding exhausts for these bikes.
RPG Exhaust