It depends on the girl. A good, back and forth grinding motion is almost always the best feeling, particularly if she has some thickness for me to caress and feel up. I have no problem letting her 'drive' while she's up there (on that note, I want the same courtesy in mish and doggy).
This isn't really a complaint, but some girls like to stay on top FORRREVER. I tend not to mind, particularly if she's doing it right up there (she probably is because I'm most likely rock hard and hitting the G-spot). At the same time, I like to my MISH on...and sideways, too.
If you've never tried that position, you've got to give it a go.