Assassin's sword is best companion/hired cavalry sword. No thrust means better usage, it's long enough to be effectively used by cavalry, and it has very good power. (47 slash, 115 length, 105 speed)
Royal Sword with Ruby is best one-hand cavalry sword for player. A bit slower and longer than Elvish Noble Sword, but same power. (49 slash, 46 thrust, 108 length, 103 speed)
Elvish Noble Sword is best general purpose. Incredibly fast, powerful, and just long enough to be used on any horse, although biggest chargers might pose a difficulty. (49 slash, 46 thrust, 105 length, 109 speed).
I really don't see the appeal of Royal Broadsword, except for the looks. Compared to all these, it's short and slow.