The M38 and M44 move faster in "free aim" (a.k.a. hip-shooting). They are also a little faster to bring to your shoulder. The loss of accuracy only starts to show up at longer ranges. Most of the fighting we do in the game works fine with the M38 or the M44. The downside is that the M38 has no bayonet (like the 91/30) and the M44 is only available on a few official maps. Also, there is the accuracy issue, but most of the time that won't be a problem for you.
In general, here's a good way to think about it:
Long range -- pick the 91/30.
Medium or short range -- the 91/30 has a bayonet, but shoulders slower. The M38 has no bayonet, but shoulders faster.
Personally, i like the M38 in close range, but I don't use the bayonet often, and I'd rather be "quicker on the draw" than an opponent with a full-sized rifle.