Um, actually, I was under the impression that the Finns didnt make any of their own receviers. My own is a 1916 (iirc) and it is hex receiver. It is a beautiful rifle.
You WANT a hex receiver.
If you desire quality and accuracy, on an open sight/iron sight Mosin variant, then the Finnish M43 wins without question. I've handled a lot of Mosin-Nagant rifles over the years, none are as nice as the "worst" Finnish I've held. Even my own Russian Nagant which has hadly a scratch does not compare to my Finn.
I dont think it matters too much which Finn model you get, just get one. I would look more at the receiver date, the date of the barrel, and the stock. They Finns built theirs for quality to be used by highly trained riflemen, not MG fodder conscripts.