Bro, use the March stats please Anyway.
Conk's toast in OU and it's actually very, very, very bad. It is very easy to wear down even with the Vest, and absorbing status wears it down further. Its speed tier is so bad it gets outsped by most defensive threats that can hit some pick off a weakened Conk. Its Mach Punch is weaker than Sash Loom's, it can't get the free turns of Spore that Loom gets, it loses a ton of health even with Ice Punch when TankChomp or Helmet Lando come in. Defensively it checks dark types and Hoopa hurt it a lot on that. Also in contrast to Loom and Keldeo it can't handle Hippo if the opponent uses Sand Offense and the lack of a secondary stab hurts. And of course it's nothing like the mixed wallbreaker that is Specs Keldeo.
Sylveon gets worn down much easier than MG Clef, can't CM-sweep like Clef because it lacks all of: a) T-Wave to cripple opponents, heal before they hit again and make them lose turns, reliable recovery like the one-click Softboiled, c) a decent way to deal with status (requires a moveslot) or d) secondary coverage to hit its checks (Clef has Flamethrower/Fireblast). And it's not the great sweep stopper that is Unaware Clef either. Specs Hyper Voice is neat, but Sylvi has nothing over, say, Mega Gardevoir other than Baton Pass for momentum plays. Pretty middle-of-the-road.
They would be cool, and really good, in UU. But in OU, they are both outclassed and don't really have much of an impact.
I'd personally love to see some of the great walls that are the Regen monsters (Alomomo, Tangrowth, Amoonguss) rise up to OU just enough. It would significantly lessen the gum-up that are some lower tiers, leave pif-stall in UU and stall cores in RU significantly weaker. Make OU a little more about stall, save the lower tiers, fair trade.
I also hope that UU tests Mega Gyara to get into the tier. Usage-wise it's already BL.