Of course it depends on the situation. An Arranger can do much more but in the right scenario there's nothing like a good sounding piano whether it be Digital or Acoustic. And to the listeners its more "real" Something they're used to hearing.
Just today I spent some time on my FP90 and was thinking about really trying to go just piano and voice. No dance music, just connecting with the crowd on a more basic level.
Hard to explain but some of my solo piano gigs have given me the most satisfaction.