My neighbors across the street from me are both glassblowers and we've discussed regular propane versus propane with oxy boost. Both of them say that the oxy makes it too hot for glass and harder to control.
In my personal experience brazing stainless steel, butane is just fine (not as hot as propane).
I have turned away from General Air over the past several years as my personal experience is that their customer service has deteriorated and has left much to be desired. I'm not going to flame them here but let's just say I don't give them my business any more.
I have an O-A rig and had the Victor torch rebuilt at US Welding a couple years ago, really happy with their work. US Welding is pretty pricey for their consumables but their rebuilds are good quality. For consumables I have been using High Plains Welding for the past couple years and have been really pleased. In fact I need to go pick up my freshly tested (and passed) refilled CO2 tank from them Monday morning before I head out to Moab.
Bottom line is, I don't see the justification for the brain damage and expense for an oxy boost for propane for brazing. I've done plenty of brazing and soldering with a regular propane torch or occasionally mapp gas and have never felt that I needed an oxy boost.