I've never played the old BMS, but I liked some of the sounds I got from the XO. Has anyone recorded an A/B of the two?
I wish I had, but the way my pedal budget goes I had to shift one to buy the other.
The main thing that convinced me (beside that incalculable "tone" issue) was this: Get the preamp gain trimpot set just-so for your playing, then give it some low G, third fret on the E string, with the sub-octave slider up. Does it fart? It probably will. The old BMS won't, it will just pump it out, regardless of whether your amp can cope or not. That is what convinced me the new BMS doesn't have the 24v nuts of the original.
That kind of weakness seemed to persist across the whole range for me. Where the old BMS would just sound remarkable practically regardless of where I put the sliders, the XO model sounded weedy by comparison. I appreciate that they are calibrated differently and the same slider positions won't produce the same results on both pedals, but the XO is literally not capable of the same fat sounds as the original. It just isn't. To me it sounds like a cheap knock-off of the original. I am not exaggerating. When you compare it to the original it just cannot compete.
I am as disappointed as anybody about it.
I should say I'm not trying to pump up used prices on a discontinued pedal - seriously I couldn't care less because the last thing I'm going to do is sell mine, I already sold an XO to re-buy a reissue - it's just the truth, they are very different and to me the old one sounds much better than the new one.
Unfortunately nobody's ever going to produce clones of it, because it's such a hilariously complicated circuit. So if you spot the difference then buy up the originals because I think it's going to be a bit of a synth classic in a couple of years.