Which is the best monocolored control deck in the format?

[Rico Suave]

However, I don't know that not beating competent ANT players is the biggest problem for MWC. Zoo and 43Lands are currently tier 1-1.5 and have similar (or worse) matchups.

Yes, it is not the biggest problem.

The biggest problem is that it has garbage for a draw engine, while something like 43land has a pretty damn good one.

[Iranon]

Against small critters (Zoo, most Tribal decks) it's fairly easy to build and play Burn as Mono-Red control. With some recurring non-creature damage source (I like Pulse of the Forge because it's only marginally underpowered as a burn spell) and a few Magma Jets to find it, you recover well enough if you are forced to throw fire at creatures.

As for Black vs. white... I think black is better set up to win the old-fahsioned way by burying your opponent in card advantage and raw power. after a Damnation, threats that kill more creatures (Gatekeeper of Malakir and Shriekmaw) keep an opponent from rebuilding. Korlash and Cabal Coffers can get ugly quite quickly. Phyrexian Arena is an easy way to keep the cards coming.

White has a bigger bag of tricks... Scepter + Chant/Abeyance, an Enlightened Tutor toolbox from Porphyry Nodes to a Painter win. I'm not actually too sold on the latter... and prefer independently useful cards that help me stabilise in the midgame (Elspeth isn't unmanageably slow if you can nuke the opponent's board every turn with a Disk).

Blue is also worth considering for a Combo/Control route. Countertop, Stiflenaught, Painter's Servant + enough cantrips to find missing pieces + free countermagic + Wastelands... not classic MUC but so full of backbreaking plays and so good at protecting them that it doesn't even need a draw engine.