I cannot vote. or If I could it would be to turn up.
As a very skilled bassist with very little gigging experience on base, I can't really say what works best in the "real world". But I'd say to turn up no matter what. Not to say that louder is better, but I notice when playing on my Fender Rumble 15 in my basement, Everything feels easier when I turn it up almost to max. I play quite aggressively, too, so it's not that I simply don't get what I need at lower volumes. The thing is, if it's too quiet, and you try to dig in to "compensate", then you get frustrated and fatigued when it's not loud enough. You feel like the lack of power is due to your playing than your amp, and you work harder to accomplish nothing. When it's nice and loud, it doesn't matter how hard you're playing, you get a nice, full-bodied sound from your speakers, and there really isn't a whole lot of dynamic difference between a light touch and an aggressive touch. Or rather, if your softest touch isn't too loud, you get used to an aggressive touch also not being too loud. You get into a sense of changing your playing style for feel, rather than dynamics. There's a "right" level for an amp for every particular venue, and sound check is for setting it to that. Your softs are soft, and your hards are hard, and you just adjust your playing to how the song should sound, and you shouldn't need to touch your amp.
In terms of an aggressive touch itself, You probably shouldn't play so as to try to push everything out of your bass as possible. I know this is sort of a cop-out word, but the playing has to be "Controlled". Like, you play a little more aggressively to add punch when your bass part is more forward, but when you're just laying down the bass, you don't need to play as hard, and just let the volume carry the strength of the sound. Playing styles should have nothing to do with volume. If you need to play hard IN ORDER to be heard, you need to turn your amp up. You never should be turning down unless your aggressive playing is too loud, in which case, everything's probably too loud. Playing hard should be that extra push for when you need the bass part to come out. Your touch should never be a blanket "I play hard" or "I play light". You play what you need to for the sound and feel you need from your instrument, not for volume or audibility.
Just what I think. Again, I haven't played Bass much in public, although I've done a fair amount of guitar and singing, but I do play a lot, so I think I know SOMETHING about how this works.
