I really hope Adam Rose would not mind me putting a link to his on-line gallery here, but I think some of his photos would be really interesting for this particular thread.
First look at the pictures here, especially the first one:
http://www.awrswords.net/pics/thumbn...&cat=3&page=22
It appears that the third type of hilt is actually the standard military hilt, adopted by the Afghan army in the late 19th century, as it is found both on the rehilted khyber and the short sword.
Then here, on the second picture there is a comparison of two khyber and one choora hilts:
http://www.awrswords.net/pics/thumbn...p&cat=3&page=9
It is a really great photo which shows somewhat of a transition from one pommel type to another. Also, note the transition in size too. The less common khybers with the bird head pommel (that is how it appears to me and I can be completely mistaken in this assumption) are shorter. Adam's picture shows that clearly, and the first one on eBay (in the order the Ariel has placed the links) is less than 20" overall, while the other one is almost 30", or one and a half times longer. There seems to be a connection between blade legth and pommel shape: for some reason it appears that the shorter blades needed a larger pommel. Probably to assist the hand for withdrawing the knife after a thrust?