Hmmm......I put the stands next to the Spectra doll (I haven't removed her from box, so I can't actually put her in one.) and I'd definitely say the 10" Skipper stands are exactly her size.
The 9" will work just as well, too---you'll just need to slide the stem up (the Kaisers are adjustable) to accomodate where their waists are. It just depends on if you plan to possibly use the stands on taller dolls, too. If so, then the 10" will fit MH and Obitsu. If you plan to use them for MH and shorter dolls, then the 9" will be best. ^^
But both sizes will work for MH, just 10" will be more 'default' MH sized:
From left to right: Barbie, Skipper 10", Skipper 9", Kelly
From left to right: Barbie, Skipper 10", Skipper 9", Kelly