Well, from my perspective, as a total outsider:
RDW <--- Midrange w/ Sweepers/Big butts (Can't rely too heavily on blockers though)/Possibly life gain, I think WX is definitely the way to go.
UB Control <--- RDW
Combo Decks <--- RDW
I'm very interested in the opinions of people who are insiders - this was just pure speculation.
The top two decks are RDW (the aggressve Hazoret variant, not random red cards shoved into a deck) and
The Scarab God based control decks.
Other decks that see a lot of play are the two (or sometimes just one) color tribal decks,
control, and
control. Most of these are "budget" decks based off of the 10 pre-con skeletons they gave us; with a
good or
control deck being the exceptions because those decks don't work without 4-ofs of a lot of the key cards. And the pre-cons basically give you a bunch of one-of rares with a single mythic per pre-con.
The only combo deck that really exists is
Fling, and that one is .... meh. At least against control. It's too vulnerable to either combo piece getting denied by removal or a counterspell; which is basically the definition of control in the game. Play
Champion of Wits; play a bunch of
counter-spells; splash red, white, or black for a win-con and good removal; and just prevent your opponent from doing anything. It's very hard to land a 5 mana (combined) two-card combo against that.
Edit: Other decks exist. I just don't see them often enough. Like I know mono
is a thing but i almost never see it.
Edit: I think
control is the 3rd best deck, losing to Scarab by a small margin.