I have too experienced some of what you say, but a little different as I play in two bands (one is classic RnR, and the other playing Blues, R&B with some soul, and jam band type music. My band has gtr, sax,trumpet, drm, vocal, and occasional harmonica. I have found the obvious....i.e. the flats sound great with some music, but the rounds bring more deffinition to most of what is played in both bands.
the flats sound great but leave alot to be desired when the bass line is very detailed. The rounds help in reproducing detailed bass lines.
The largest influence on how much Bottom End, or Tone for that matter, that I get seems to lead more towards a discussion on finger technique rather than strings.
Regards, Robbie