To be brief, as I must for fear of board-post-munching: I compare the average full attack damage/round for a 18 Str 20 Dex Lvl 12 Fighter. Feats of TWF, iTWF, gTWF, WF, gWF, WS, gWS, iC for short sword (SS). My argument: better off wielding two extra damage SS than equal value Plain-Jane...