Uh, actually neither Reimu or Sakuya's clean focused shots bleed power. Only Marisa's does iirc.
I just tried it, and yeah, MarisaB is the only one to get power while focused.
If there's any comparisons I can make to these characters, it seems like
ReimuA = MoF MarisaC/IN Remilia in terms of covering attack area
ReimuB = Ten Desires Reimu (although not as potent as other post-MoF Needle Reimus)
MarisaA = The bomb type. You don't use it for the shot, you use the bombs and you use them liberally.
MarisaB = The new post-MoF Needle Reimu in terms of shot damage
SakuyaA = ... PCB SakuyaA, except actually capable of damage
SakuyaB = PCB ReimuB, though her focused shot is very narrow.