One word: crossover. If you are biamping your mixed drivers or using a crossover to prevent different drivers from producing the same frequencies, it's a whole different ballgame, like a good FOH. Putting a 210 or 410 on a 115 sends all freq to both cabs=not usually optimal out in the room, although it will sound great from close up. How you sound on stage or from any 1 spot in the room may have little to do with how you sound at another spot. Unless you walk around the room and listen from multiple spots while playing, you really don't know how you sound "out there" at all.