At louder volumes the "thickness/heft" of the ABM comes through above the sound of the RM, so the bass would more than likely sound "bigger" - or at least that`s been my experience from using those two amps. The ABM sounds louder when in fact it`s that the sound just has more depth to it, giving a greater presence.
As has been said though, you don`t want your on-stage volume to be so much louder than the rest of the band, so going though the PA not at a louder volume than your amp less will still give a better spread for the bass. I`d also in this case consider removing some of the low end for whatever goes through the PA.
And after all that, if it`s not worked, buy those subs!