Honestly I would recommend comparing the weapons abilities, style, and look. You can do this all back at the villa, along with practicing with each weapon. I personally recommend the Sword of Altair for overall quality and the Sultan's Blade for look and ability. But many other weapons and combinations are worth using.
I'm not a fan of the bigger short blades. They just don't have the feel of Altair's and the animations look strange(especially with the butcher knife). The stats of weapons in this game are almost inconsequential, since the outcome of any battle is determined by the skill and tactics of the player.
i think they could have made Altair's sword look much better. the Schiavona is the best looking sword IMO, and its just about as good as the sword of Altair. the war hammer you get after collecting 50 feathers is also great. it offers different moves and counter attacks. i really wish you could equip and keep the larger weapons, like that broadsword and those axes.
for secondary, id go with the notched cinqueda. the other high end ones are fine too.
if your looking for the best weapons, they are usually the more expensive ones. but as you play the game you will gradually acquire a ton of money (i have over 1 mil) and the prices wont matter.