Who cares if she’s dressed or not?
Somewhat stated above, but when done right, a naked attendant will give much more of a body to body contact experience, and it's fun, even face down with eyes closed, to imagine what parts are softly brushing over your back, etc. and +1 on the feeling of having her straddle your back naked. That's a winner. Somewhat the same with the sundress sans pantes. And of course, everything depends on her attitude. If she's fun and playful, a good time is likely in store.
Now where are these pantyless sundress spas I've heard talk of? Recently, everyone is into the lululemon jogging pants look. I love to follow that down the street, but it makes things awkward in the session. Anyone?