Thanks for showing this great group of daggers with a nice, but puzzeling mixture of traits. You obviously know more than I do about these Saudi Arabian daggers, but I can speculate a bit. To me, the name question is less important as names and categories were made up by collectors to order their inventory and often do not correspond with local terminology.
Wheather made in Mecca by makers from Ha'il, or made elswhere to the north, they definately reflect influences from Jordan.
The style of decoration is not Jordanian/Palestinian, but many elements are, like multiple decorative rings, insets of stone/glass beads, central band on the hilt and more. The blades are shibriya (diamond cross-section) without the typical recurve) or Jambiya (second from left) and even show some dharia traits like the fullers on the leftmost one. I would think that this style originates in northern Saudi Arabia. In mecca, it overlaps with daggers and influences from the East (Dharia) and South (Janbiya).
The large, dark shibriya, second from left in your forth picture, is clearly a Jordanian shibriya, regardless the size. I have shown in a recent thread (http://www.vikingsword.com/vb/showthread.php?t=22301
) a shibriya of almost 40cm and I am sure that even larger ones exist. The inferior quality of the blade, common in later Jordanian daggers is clearly visible in the 3rd picture.
The "twins" are a whole different story. I have seen several of them recently and I think that they are older than all the rest. Big metal studs are an early feature (see photos in my previous post in this thread). However, as far as I know, they are not similar to early daggers from Sinai or Palestine. They do show very general similarity to Marsh Arab janbiyas, so it is very possible that they are also from northern Saudi Arabiya, or alternatively from south-west Iraq, or even from the Syrian desert.
The last group is all Jordanian shibriyas, as you probably know. Some are early and good quality like the two "horned" ones. The oldest is the rightmost one which has a "normal" curved blade. The scabbard is an old replacement. I actually wanted this one, but the dealer refused to send it to my country. Thanks again. This is an original group that we all can learn from