I'm going to have to say Scizor. Scyther can't really do anything super-effective (to my knowledge) to Scizor, while Scizor, like Chromas said, gets a super effective Aerial Ace or Wing Attack.
I like Scyther more, but there's no doubting Scizor's got 'im. D:
I'm generally unlucky when I use metronome. Although, I did once get Judgement, that was pretty awesome.
My friend almost KO'd my Gardevoir once with a Togepi by getting Extrasensory, Earthquake, Flash Cannon, and X-Scissor in a row. Gardevoir also flinched from Extrasensory because she was...