Who is more of a nut? Definitely Paulie. I don't think Furio is crazy at all. He is a cold, calculating enforcer who goes about his business is a ruthless manner.
Paulie, on the other hand, has a definite violent and crazy streak in him. You never know what he might do if provoked in the slightest.

"Keep your body strong, your blood clean, and your mind sharp and mean." Henry Rollins