the longhammer is a special orcish hammer that has an enchantment to make it swing faster then a greatsword but cant be unenchanted.
the rueful axe is a daedric artifact and a reward depending on what you do to complete the quest...the other reward is the masque of clavicus vile
meh, I never saw the longhammer, where do you get it.
I got the rueful axe, but my other weapon for both my characters did more damage, so I did not use it. Also, for my first character, I didnt limit myself to evil things, but if there was a choice, I would choose the good option, for my second character, I was aiming for the Oblivion walker achivement, so I did turn it in, although, if you really liked the rueful axe, you can always stall the quest until you find a better weapon