I recently wrote my undergrad dissertation on the Lee Enfield in the First World War, so a similar sort of thing really. Sounds like an awesome project!
For my money, the Mauser gets it, I can't really think of an area in which the Mosin is substantially better. Both are generally accurate, reliable and tough. The Mauser is generally more accurate, no less reliable and equally tough. The Mauser has a better, smoother bolt with a nice controlled extraction . . . there is a reason its action and variations thereof have dominated the sporting rifle world.
The Mosin was good when it was designed, for what it was designed for, arming Russian conscript armies round the turn of the 19th Century. It performed sterling service in two world wars, as did the Mauser. The Mosin is a very simple piece of technology, ideally suited to mass production and citizen armies . . . but its not like the Mauser is difficult!
All round, the Mauser is a better rifle and is surely one of the all time classics of firearms history. Well, thats what I reckon anyway . . . and I have only shot these rifles a couple of times, would love to own them both one day.
Good luck with your project!