Did I miss something "special" about this bayonet?
Between the two full tang variations, I would say that the threaded tang should be valued a little bit more than the riveted pommell.
As stated before by Bill, there are probably less examples of the former, due to the fragile system of the tang.
Also (but this is my very personal opinion) when you buy a
full tang M9, the first thing you want to do is actually .... to take a look at the tang and show it to your friends/collectors, something that can't be done with the riveted pommell version.
You know that there is a full tang under the pommell, but you will never see it.
Of course, the example shown by Chris on this forum, with the tang not riveted, is a real prize!