I'm curious, why? They all have the same base damage (1-10, 5,5 average), the same critical damage bonus (19-20/x2 in bastard sword and katana comes to 1,10 damage multiplier over time, same as x3 for the dwarven waraxe). I understand one may prefer more frequent criticals over more damaging ones, and so the bastard sword and katana would be better than the DWA, but why katana over bastard sword?
Also, to Claudius:
What is it for? Dual wielding, sword and board? Because if you're going pure damage and you have a high strength, maybe you should consider a two-hander, and in that category, I'd say the scythe knows no equal. I once did a main bard with Red Dragon Disciple and Champion of Torm wielding a scythe (this was in HotU), and that was my best char by far. Very buff dependant, though, so it took a while to get trucking, but when it did... Oh my god.