To get a vorpal weapon, you not only have to roll on the Major weapon properties table, you have to roll an 89 - 90 in 3E.
To get a disruption weapon, you have only to roll on the Medium table (76-78) or on the Major table (47-49).
(And that's without getting into what type of weapons those properties are allowed on).
But I'm seeing vorpal weapons drop like they occupy a good 10% of the loot table, and . . . let me check. . . I don't remember the last time I saw a rangen disruption weapon drop.
What I would like to see in one of the next couple updates is a return to more proper loot tables, as per 3E.
http://www.d20srd.org/srd/magicItems/magicWeapons.htm