In that post the only Obitsu head is the rooted brown one on the 21cm on the far right a type 4 so it's one of the "bigger" ones, the elf ear one is a Noix de Rome. The only other Obitsu head I have is on my Slim, it's about the same size as the elf ear.
My general girl comparison page is here
http://dolfielittles.com/girls.html in the upper left of the page is a pull down menu that says Little Encyclopedia, it leads to the different brands like Mattel and Obitsu. You can find a boy comparison page off the main encyclopedia pag.