If your meta is heavy aggro (Zoo/Affinity/Goblins/GW), then 2/2 split. If your meta is mostly 8-10 creatures/deck, play Jace. Jace is terrible against Zoo/Goblins/Merfolks unless you have a way to support him (Peacekeeper against Merfolks, enough counters against Zoo's Burn i.e. difficult considering you still have to keep dudes off the board, and Jace is just not very spetacular against goblins when he faces Ringleaders/Matrons/Siege-gangs etc).