I think that as long as there is a related weapon, you can achieve both. For example, if it is a type of sword, compare it to an already included sword of a similar weight and size. If the sword is near the size of a bastard sword, go with 2d4 or 1d10 damage. If the real world description implies something more (based on the quality, weight distribution or enhancements like serrations) then you could add 1 to the damage or rule that this weapon is only available as a Masterwork weapon (+1 to hit).
I voted: Stat it realisticly then place its simple/martial/exotic catagory to balance it.
So, I would add the ability to categorize the weapon to my opinion above.