Well, in some specific situations regular Jessica worked better.... VERY limited ones. Part of it was that her attacks had different tags. As Kuurth some of her stuff was considered magic, cut as spiderwoman her basic melee action was tagged as unarmed. Which meant certain build ideas couldn't be used on both... but more importantly... effects that protect you from magic(Magic Warding was a pretty common one to see in PvP) will greatly diminish Kuurth's special effects.
But the special runic powers are a massive advantage... Rune of Ruin especially, if that gets used on you a lot of the time you'll just die. At any rate, Kuurth was nearly always better... nearly....