Why don't we do a list of "known" issues with both designs?
Mosin is known to have trouble feeding, due to the rimmed case. There are fixes, but it is a known problem.
Mosin is known to have accuracy issues if the bayonet is not mounted and extended (with some models)
Mauser.... I don't know of any "known" issues with it. It feeds cartridges like butter, no matter how energetically (or not) that the bolt is cycled...and accuracy is not dependent on any accessories being mounted or not..
Controlled round feeding and an extractor that grabs a HUGE amount of rim should make it quite a bit more reliable under battle conditions.
In "dangerous" situations, the Mauser style or its variants are nearly always the choice. Dangerous game rifles (bolt action) nearly always require controlled round feeding and a mauser style claw extractor. I have NEVER heard of a dangerous game rifle being built on a Mosin action.
Like I stated earlier, I really like the Mosin, but if I had a choice between those two rifles to carry into combat, I would choose the Mauser everytime.