Overall I'd say that the old tail would easily empower the lightning gun with static electricity over the new tail.

Still, there is only one true way to decide which design is better. Have the two characters fight it out.

This is of course only done in the name of science, and my incessant need to see foxy female femmes fight furiously for future....

Oh...oh...oh, I mean Cunning Killer Coon Chicks cavorting curiously cool Weaponry.

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Can you tell I really need sleep?

I must agree with ratsmith, I like the longer/fluffier tail better than the shorter one.
The longer looks more coonish as opposed to foxish.
But that's just my opinion.