That really depends on the condition of the 91/30 and what has been done to it to improve accuracy. The same applies to the PSL as well... some PSL's are more accurate than others.
Let's say you get a Finn M28 Mosin, it may be more accurate than a 91/30 or PSL. A M39 Finn might be more accurate than a sniper 91/30 as well. The 91/30 does have the inherent advantage of being a bolt action weapon, which is a design that is likely to be more accurate, but if the barrel isn't as good as the PSL, then the action can be the best in the world and the gun still less accurate than a PSL with a great barrel and good head spacing.