What sword should i upgrade?

Hey, i'm soul level 25 on a character that i mostly level endurance and dexterity on. I'm heading in to "Depths" now, which means that i have access to the smith in undead parish. I love the short swords fast attacks and kick, so i have been using that since i first got it in the burg. Now that it is time to upgrade however, it seems that i should use my shards on a more viable sword. Which would you recommend me to use and upgrade? I am grateful for any help, Thanks!