I have em all, tried em all and I'm still using the knightly arming sword.
It's 97 speed, but you're not going to outspam anyone anyway. If you can outspam someone with a 101 speed 1h, you can do it with a 97 speed 1h too.
The thrust on the KAS hurts. Badly. Especially when placed in the face area. The long espada does the stabbing job even better, but I would classify that more as a specialist sword. The low cut damage on swings means you have to stab more often, which is harder to do than just swinging your weapon.
The KAS is also very useable from horseback (if you ever want to play mounted that is) and can be used perfectly fine without a shield (swashbucklin style).
I wouldn't use any other sword than the knightly arming sword (or the long espada eslavona when I feel like it).