M38 or M44

If you're only going to get one & not round out the Mosin collection later then I would go for the 91/59. It looks the same as a M38 however it was made with cut down 91/30's well after WW2 (1959 oddly enough ). From what I've read they are the most accurate of the carbine versions. They do cost more than a 38 or 44 but the one that I got from AIM was in beautiful shape & is a great shooter.

There are 91/59's with a hex receiver (either Izhevsk or Tula) however they are much rarer than a round receiver. Which makes sense when you consider that the 91/30 that it came from would have had to make it through WW2 reasonably intact to be cut down in 59. Most of them are probably late WW2 production that never saw much service (mine is an 1944 Izhevsk on a M44 stock with an arsenal splice repair on the stock).

Sorry, I thought AIM still had them listed when I sent you out on the hunt for one .