PvP for instance is much about one hit then back off and not so much about dealing out a consistent damage, PvE is a mix of both where you might benefit from a faster swing time but still want as much damage as possible per swing.
I have done a lot of analysis on this (spreadsheets, swing time, stamina cost etc) and this is basically a list of weapons that has a high damage per swing and a high dps...
Greatsword of Artorias
Black Knight Great Axe
Stone Greatsword
Murakumo
Great Lord Greatsword
Bastard Sword
Claymore
Dragonslayer spear
Queelags Furysword
Ofcourse since Murakumo is buffable its probably the best one but I was surprised how good the Bastard Sword was.
The Dragon tooth should take an honorary mention, its really low dps due to its long swing time but since its buffable it does a significant amount of damage.