The differences in the Physical ATK in the later levels, become VERY significant, between a Sword and a Blade.
For example...
A plain, Level 72 Devil Sword has a Physical ATK of 588-708.
A plain, Level 72 Blade Blade has a Physical ATK of 626-728.
It makes even more of a difference if you have an SoS, SoM, or SoSun.
See for yourself:
http://sro.mmosite.com/database/items_weapon.shtml