Silent Nightblade has more DPS but less damage per hit. SN can also be charge spammed because it doesn't slow you down while charging and doesn't leave you super-vulnerable after you use the charge attack. Also, since you often won't be using the 2nd swing on a Faust (because it leaves you so vulnerable), SN's DPS is comparatively even higher. It's true that SN has slightly less reach and knockback, but if you can't kill slime and gremlins without more knockback, something's wrong. Personally I'd go with SN (as it's what I have).