MSPeconomist

If you're willing to pay extra for lounge access, I would highly suggest Prince Gallery, although it's not a great location IMO. However, a lot depends on how you plan to travel to the airport. I tend to pick hotels in Tokyo based partly on the limobus schedules as I consider having door to door service (at a reasonable price) to be a big advantage, but I don't want to be forced to depart extremely early due to infrequency of schedule.

Second choice for lounge (also paid) would be RC but I personally don't like the location.

I don't know the Conrad (aren't there at least two of them?) or its lounge.

With top tier Hyatt elite status, PH is nice and for others Andaz (which offers happy hour for all in its lobby lounge). Here we're talking about lounge substitutes rather than actual lounges. I'm not really a fan of either location.

IIRC Imperial has four concierge floors at the top of the older main building, with hostesses in kimonos, but no lounge. However, there is some early arrival/late departure waiting room IIRC on the same floor as the business center, which offers coffee and tea only. I like the Imperial's location (almost next door to the Pen). The pool seems dated. It's also a large hotel, so most wouldn't consider it to be true luxury. Normal lines to check in/out can be long, but then staff bring chairs and beverages.