Since you can't synch and you don't have any guaranteed IVs, you should aim for +Sp. Atk. or +Spe nature and 30/31 in Sp. Atk. and Speed, or a Hidden Power, instead of good IVs overall. Vivillon usually runs Focus Sash anyway.Pokéball pattern Vivillon - #666 (Modest) : 26 / 31 / 30 / 19 / 26 / 31 HP Ghost
Keep or toss? I'm leaning toward keep. It's literally the best one I've gotten, and the only one I've received that is rated as outstanding by the judge.