Between the two of them, IMHO the two best sniper rifles of WWII, there isn't a lot of practical difference. The raised, add on, cheek piece makes the No4 T more ergonomically appealing but they are both similar in accuracy, repeatability and reliability. The No4 Ts were selected for accuracy first and then built into sniper rifles. The later war time production Mosins were just taken off the line and made into snipers before testing for accuracy. An interview I read of one of the Russianicon producers of the Mosin sniper rifles said there just wasn't enough time for such luxuries and that they were confident in the Mosins accuracy right off the line. That speaks volumes. The Russians fielded more snipers than any other nation during WWII.
To show how highly the axis forces regarded the M91/30 sniper rifles, all that were captured in serviceable condition were reissued or stripped for parts to keep their existing rifles operational. They liked the PU scope so much that they used its design for the basis of their ZF4 scopes, bases and mounts.

As far as the scopes on the Mosins being to high, that was pretty much standard practise for European sniper rifles. Even the No 4 T scope is to high without the cheek piece.

Personally, I would think that in trained hands it would be a toss up of which would be the winner.