I thought the 12/15 stack was a little more forward than the 15/15 stack, and had great cut with a band. The dual 15s have a little more low end, and are a touch smoother in the mids. I sold my 12/15x stack and kept the 15/15 stack. I still use my dad's 12/15 stack (with EV speakers) frequently. It's centrally located in our practice space, and I aim the 12 (on top) at the drummer and the 15 towards the rest of the band. He can hear my attack better through the 12 and we can play tighter. Last gig, I brought my 15/15 stack for the audience and an EA Wizzy10 for the drummer.