Vibranium is more durable.
As to the second question,it all depends on the quantity and the purity. A large very pure piece of Nth metal like say the clawnof Horus offers greater benefits than an equal size piece of Vibranium. The Nth metal of say Hawkman's usual gear (like Mace etc) doesn't.
With a pure piece of Nth like the claw (whichbis extremely rare) and the right knowledge of how to use it you can control strong nuclear forces so you can matter manipulate, as well as gravitational and magnetic forces (as was done by Ominar Synn). With a small amount you can negate gravity to fly or boost it to strike and absorb energy (like heat, blasts etc). Vibranium can do what the small impure piece of Nth can more effectively. It can't do what a large pure piece can
His mace isn't made of Nth, it is laced with Nth. The amount of Nth metal in it is about 5%.
Nth metal is very rare. An entire Thanagarian cruiser uses an amount that is about the size of a football to power and reinforce it. That amount is spread throughout the entire ship.
It also enhances the senses of someone who has been consistently near it. Enhances physicals to a little above peak human, can be used to track energy signatures, bolus the gravity manip stuff.
On the healing side of things HM had his caroted artery cut and was quickly bleeding to death, he asked to have his wings but over his body (which he wasn't wearing when cut) and healed in a few panels.