Yeah, I vary the mix to the rotating speakers, different songs demand different rot sound. Sometimes subtle, sometimes more evident. It makes the other modulation pedals shine more too. Flangers and phasers sound so much better when adding it.
The reasons to return the sound of the rotating speakers to my system (Axe) is to have full control of my guitar sound. If the rotating speaker microphones go straight to the FOH mixer, first I need 4 more channels in the main mixer (and we use A LOT anyway!), and our sound tech would have to mix the signal himself with the non-rotary part of my sound.
I'm the one who knows exactly the amount of rotary sound I want in each patch, so I feel safer giving the sound tech just the two L/R from the Axe.
Same with my keyboardist, he uses his own 8 channel mixer to supply just L/R to the FOH. If our tech would have to mix everything he would become crazy and he would need a monster mixer table.
About stage volume, we keep everything quite in control so our tech can make a nice mix (we all use in-ears except the other guitar and saxophone player), so the only sound comes from his monitor, the drumset and another monitor I use for guitar feedback and sustain. Adding the rotating speakers to the equation is not adding too much.
About comparing it to the Axe's rotary, well, it's just not my choice for rotating sounds. YMMV, etc.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I just like the way it makes the sound wider and "chewier" (hard to explain), like Comfortably Numb solo or like here in "Run Like Hell":
http://www.youtube.com/watch?v=9CfZQVtnZYQ