It's brand new, so full durability. In fact my Saw Cleaver is nearly half (do the damaged done by them go down I take it?).Did you check it's durability? maybe it needs repair? Either that or check the runes you have attached on the other weapon.
Are you using thrusts/blunt attacks on one compared to the other?
Enemies can take slightly more damage from one compared to the other. There's no "slash" in this game so I assume "blunt" covers everything that isn't thrust.
I'm essentially doing "slashes" with normal attack for both. Guess this would be the Blunt part. Maybe just that enemy that they are very similar. Just little annoying that the Saw Cleaver does same damage-ish at faster rate. I'll have to try it on different enemies.
At least the claymore tricked version of it does a lot of damage compared to the tricked version of Saw Cleaver.