No question I'd take the Mauser. I don't buy guns for investments, and it sounds like you're looking to use yours instead of holding it until it's worth more than you paid.
The mauser has a better/smoother action, better trigger, better sights. There are tons more options for mods available for the M48.
And one thing that should not be overlooked is the MUCH better safety on the Mauser. If your going to be hunting with it, you want a safety that can be easliy flipped, not the clumsy knob of the Mosin.
NRA Life Member, SAF contributor.