Ive got a few Zoom boxes (had the B3, but now B3n). Ive also got a Spectradrive (my second).
If i had to chose one to play live with it would be the Spectradrive. It has a really nice solid tone, and i love the EQ. (This spurred me on to get a BH800). The comp in the SD is of course very good, but i agree with DB that the drive side is quite poor. It does have a good tone print that works as a boost though. The only TP i use in that slot.
Again, like DB i dont really get on with the Zoom menus. I can get through them, but just never found them to be well thought out. I do love my B1-Four, but I wouldn't use it like. I haven't touched my B3n for a couple of years.