Two separate questions here.
Most efficient? - definitely Yuki @ Ginza.
That girl is so switched on, and efficient, and totally in control of everything.
Hottest? I dunno.
I go to a shop for the WLs, not the mamasan.
Yuki is definitely hot. Fuck yeah she is hot.
But is she the hottest?
Maybe not, there are probably younger and hotter mamasans ... but she is definitely hot.
Put it this way ... if I turned up to Ginza to see a 19yo gorgeous Japanese JAV star, and Yuki said you have a choice, you can have her, or you can have me, I would probably choose Yuki.
But its never gonna happen ... so yeah ... whatever ...