Are you more interested in a "shooter", or a collectible?
There is often overlap, but a rare Mosin with a so-so bore (or worse) can have greater value than a great shooting, $100 Russian 91/30.
I would steer towards the Finnish Mosins, because they generally have better fit, finish, and accuracy.
Be aware, that these sometimes have true .308 groove diameters, while the Russian and others more commonly have .311-.312, or larger if worn.
Go through the site suggested above. There are also several forums that specialize more on the Mosin- and by all means, do a search here, and check the C&R section for threads on this great rifle.