Now I haven't given this much thought so bare with me.
As a mole I would get to run around on all fours. It would be frightening running along the kerbs of the streets watching the cars hurl by with random turbulance, but I think the thrill of it alone would be enough to justify my existence as a mole.
Whats more is I would be very light and small, I would see the game from a completely different perspective. Being light would be nice and it would be fun to examine new objects with my front paws. I wouldn't have to deal with the stresses of leveling up my mole to buy new clothes that I don't really need, or buy weaponry or accomodations. I could live anywhere, go anywhere, live out my hearts desires.
It would be fun to leave the city as well and visit Blaine County and get lost in the huge dome of infinite microscopic detail that I would have to traverse. If I could tunnel into the mountains that would be brilliant, I could live in the sides of Mt Josiah far away from the tedious boredom other players have to endure to simply generate a moment of joyful serendipity in the cesspool of human contact.
Yes, to be a mole, thats the life for me.