IMO The doubters are clueless about the 100% uniqueness of a postive displacemnt supercharged (P/D S/Ced) engine.
The HP from a positive displacement blower is solely dependant on the blower displacement/internal pressure ratio and the pulley ratio.
You can make less power with a larger blower by simply pulleying it down to move less air than the smaller blower.
You can make the same power as a smaller blower by running a pulley ratio that moves the same amount of air.
You can also up the boost and make hundreds of HP more than the smaller blower could ever possibly hope to make.
Forget about headers, exhaust, all of the normal stuff you think of to make power on non-PD S/C engines. The P/D S/C alone determines how much HP is made by how much air it moves. Everything else is secondary or tertiary at best.
The only 2 things that truly matter for performance on a P/D S/C engine is 1) pulley ratio and 2) do not starve the intake side of the blower. Get big intakes, air filters and T/Bs to maximize power. Exhaust side improvements are nearly meaningless compared to just upping the blower speed a bit more.
The larger blowers allow you to move more air with less input power and less ouput heat (ie more efficiently)- so if you want to turn it up, the larger blower is always better.