There often aren't such differences; hence you can sell the more expensive item. Then again, you don't need money for much in the game, and if you need some, you can sell some of those excess Dragon Stones you've been carrying (there are far more found in the game than you are realistically going to actually use, to the point where you will find yourself discarding them, leaving them behind, or using them when you can't get the full 20 power).

Sometimes, items with the same name may have different properties. For example, I believe there's one piece of Magic Chain that is more expensive than the others, but it has 0 charges of Zak's Speed. (0 charges means you can't use it, but you can use the Charger spell to add charges to it.) Zak's Speed, incidentally, is really good, especially if you stack multiple casts of it.

Also, keep in mind that every 5 points your Strength is above the minimum gives you +1 damage. This makes the Ruby Dagger better than the Shortsword, for example. (At 8 Str, Ruby Dagger does 1d4+1 with +3 AV, Shortsword is 1d6 (same average) for +1 AV).

Incidentally, unarmed combat (I believe the skill is called Fistfighting) is very good in the early to mid game. Put a few points into that skill (at only 1 skill point per point in the skill!) and your bare handed attack is far better (and more consistent) than most of the early game weapons.

One more thing, there are a couple special bows that can hit multiple times, but only if you choose F)ight rather than Q)uick fight.