I'm returning to gigging after a long (15 year) hiatus. I have a Mesa M-Pulse 600 which is a single channel amp with a choice of active or passive inputs. I will be using two active basses, one fretted and one fretless. I'm trying to decide between a mixer (Raven Labs MDB-1) or an A/B switch to allow for quick changes between songs. Are there any advantages of one over the other? What do you use? Thanks in advance for your input!