Black cat/mercurial or skolver?
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That's very arguable. Neither appears to be the more popular choice and neither really makes more sense.
Either are good to use, but I'd say BKC/Mercurial Mail(?) is better; you'll gain flexibility with weapons with BKC and have slight shock resist with Merc. Only thing I think you're losing over Skolver is freeze immunity which is not commonly spread status vs. shock, +1 DMG bonus on swords which is kind of minimal, and piercing defense (though I doubt a clean Skolver set will protect you from piercing anymore than BKC/Merc.). Oh, you also lose your stylish fuzzball look, most definitely consider that.
But really, you should remember to adjust your defenses to your opponent's weapons and playstyles; it wouldn't be a bad idea to have both readily available.
Wrong section or wrong section?