Well, just looking at my own personal collection of sharp pointy things, I find evidence of reason for the 3.5 weapon size rules, dislike them though I did at the time they were introduced.
Among the blades I own are an actual dagger and a miniature scale model of a sword that are both the same length.
The dagger has a handle that fits my hand, and a nice, broad (if short) blade that is more than 1.5" across at the hilt. Its proportions are about 50% blade and grip. This is clearly a human sized dagger.
The scale model sword has a blade that is about as broad as 2 pencils at its widest, and its "grip" only fits a few of my fingers. Its blade is much longer than its grip, and it also doesn't weigh as much as the dagger. This would be a Tiny longsword or bastard-sword, in game terms.
Among the blades I own are an actual dagger and a miniature scale model of a sword that are both the same length.
The dagger has a handle that fits my hand, and a nice, broad (if short) blade that is more than 1.5" across at the hilt. Its proportions are about 50% blade and grip. This is clearly a human sized dagger.
The scale model sword has a blade that is about as broad as 2 pencils at its widest, and its "grip" only fits a few of my fingers. Its blade is much longer than its grip, and it also doesn't weigh as much as the dagger. This would be a Tiny longsword or bastard-sword, in game terms.