Sliding Tray, definitely.
My original housing was the Subal Miniflex for the F801S - no tray, camera screws into a plate inthe bottom of the front half of the housing. My housing for the Fuji S2 uses the same sliding tray in front half that i believe all the newer Subal SLR housings use.
There's no question whatsoever that getting the camera body in and out, alignment, etc. are much easier with the sliding tray. It lives in the housing, so I'm not likely to leave it at home. The lens release lever is the other big plus, making it possible to switch lenses and ports without removing the body from the housing, something that is difficult or impossible with some large lenses with the F8101s.
Regards,