Which one: 8mm or 6.5mm?

If you wanted to buy a 91/41 for a collector and a shooter but had to choose between two rifles that were pretty much identical except one is in 8mm, which one would you get and why?

I'm thinking 8mm is cheaper ammo to shoot and there is also the possibility of a rarer gun if you believe the story about the Italians conforming to German ammo standards during the war, but to the contrary I've also read that 8mm conversions were actually postwar...(?) On the other hand, 6.5mm is truly Italian, but the downside is ammo cost.