It kind of depends on the goal of the session. Is it to torture the lee and make them have a super intense experience? If so, a table is probably better cause you can stretch and immobilize them much easier. Not to mention better if you want to use oil, lotion, etc. cause you don't have to worry about staining bedding. Also, a table makes the lee more accessible if you want to have multiple lers or something like that. You can also attach stocks to a table for added intensity.
But if you want them to have a more playful or sensual experience, you might want a bed so the lee is more comfortable. That way you can sit or lay near them easier. You could also give them light tickles to help them sleep and they wouldn't even have to move!