No developer is more important than artistic content. But there are subtle differences...
I used D76 for a while then moved to (primarily) Xtol 1+1. The sharpness/speed/graininess are all just a tiny bit better than with D76, but you need to be looking at prints side-by-side to tell the difference. D76 achieves smoothness by smearing grains whereas Xtol seems to just not grow them as much, so less softening effect is required. The net result is both increased resolution and decreased grain: I can get a grain-free 16x20" print from 6x7 TMY2 at EI800. Even at EI1600, there is only the barest hint of grain.
Xtol is also far more convenient in the Jobo because I need only 75-100mL stock per roll, not 150-250mL. That matters a lot because I put 6 rolls in the tank, don't want to develop at stock concentration and need to keep the total volume to no more than 1L. With D76 at nominal capacity, I could develop only 2 rolls at a time and that would really suck.
I also use Rodinal for fine slow films. The tonal curve is quite different and I use it when aiming for a particular low-key look that Xtol won't give me.