Years ago I had collected nearly a dozen KTM mufflers for my 125 and 300 bikes.
Due to the nearly standard frame, they were easily interchangeable.
I had stock (hockeysticks), shortened stock and aftermarket silencers.
A couple of things stood out, the 125 favoured shorter mufflers, the 300 longer for both power and noise.
Shortened mufflers tended to produce a sharper, higher pitch noise than their longer deeper pitched brethren.
My favourite mufflers for the two bikes ended up being a Pro Circuit 304 shorty for the 125 and an Enduro Engineering EE3 for the 300.
I think the performance differences were more related to rpm than displacement. Where the 200 Blaster engine runs closer to the 300 in rpm range, I think a longer silencer would be a better idea. That said, the performance differences were slight, but the noise differences were severe.