What should I run? Bant? Grixis? Jund?
It's personal preference
Play style?
It all comes down to why type of player you are, what kind of deck you do best with/have most fun with, and what deck you want to use.
Some suggestions of top tier decks for different play styles:
-UW Human Aggro (for the player who loves early creatures and not a lot of spells)
-Bant Control (what appears to be the best control deck out there right now)
-BR Aggro (Similar to UW humans, but with burn and direct damage)
-Jund midrange (For true spikes, this deck is everywhere, and has insane creature power through thragtusk, and Olivia Voldaren, while stacking up on all the removal possible)
-Junk Reanimator: closest thing to a Competitive standard combo deck you can get. High risk (GY removal is in 99% of SB's right now), high reward (T3 Angel of Serenity)