Really, the choice of weapons in-game should rightly be determined by the time frame of that particular engagement anyway.
In any case, though, if game mechanics could be modelled for real sticklers for detail regarding rifle availability, there would be a percentage of 91/30's, a percentage of '44's , etc. with the great majority probably going to 91/30's all around as they were (and still ARE) a proven weapon with a long production history.
Personally, in-game I tend to err on the side of historical and prefer a 91/30; I'm not so sure the game mechanics are to the point where accuracy in-game is affected by a fixed bayonet, but from my own Real Life (tm) experience the only effect the extra weight up front has is to get my sights back on target a fraction of a second faster. Certainly, line troops would have fought with bayonet fixed as a rule, but their engagements were really not meant to be fought at much more than close range anyway- so bayonet 'harmonics' and all wouldn't have had that much of an effect anyway. As for snipers, they wouldn't have had any reason to fix a bayonet as the added weapon length would have only been another thing to advertise their position, and since they sighted in with the telescopic sight anyway, whatever non-bayonet residual 'barrel warping' there might have been would have long been compensated for.
(BTW: jgsales.com has MN 91/30's for under $80, with sling, oiler, bayonet, take-down tool, and dual cartridge pouch. All you need is a C&R license from the BATF <$30 for three years> and they'll ship it to your house. Or grab one from a gun show for about the same, extras maybe included. Either way, you'll be getting an arsenal refinished weapon that has probably seen combat somewhere from the Spanish Civil War on up, and most likely in the Great Patriotic War. I presently have a M-1 Garand, and I will soon be adding at least one MN 91/30 when my raise hits next spring!)