The difference is noticeable but certainly a matter of preference. Most players with any of those masterwork weapons rarely pick up any one of the others. The only weapon which seems to stand triumphant above the rest is the MW long espada, but then again it's pretty expensive and a comparatively boring weapon. If we want to overly simplify would could push them into some niches:
Gross Messer - devastating close combat infantry sword
Elite Scimitar - cavalry sword, off-hand weapon for bowmen, supporting sword
Italian Sword - somewhere in-between the other two without significantly out-doing either of the them except in terms of versatility
Long Espada - cavalry sword, close combat sword, anti-tin can sword, anti-horse sword, nice off-hand weapon for bowmen, supporting sword
It used to be that the disparity between non-side sword/long espada's and the top two swords was so great that almost everyone used one of the top two. Now the devs seem to have struck a fine balance which affords far more interesting diversity. I'm happy about it
EDIT for new post: Kan I find it's a good weapon but not long enough for a pure cutter. Perhaps I'm just inexperienced with it.