Enlighten me why you would want less suction 
Chris
you mean less suction in parallel ? true
well , when the wand is on the carpet , the operational suction will end up pretty similar in both series or parallel . So having the ability to switch is not necessary as such , there might be certain carpets where wand contact is not ideal so one may out perfor the other on some particular carpet or wand type .
From a machine sales point of view it might be a good move . Those who might be looking into the whole series vs parallel thing can have both without deciding .
