Depends on the map really. Generally for me I'd say omen on everymap apart from breeze and pearl. This is because omens smokes have a lot of advantages to them like how easy it is to one way, or how that the smokes recharge making it easier to use in retakes,rotations or even fake smoking. They also have a very long range. Other than smokes omens util allows it to be used aggressively if needed in different situation and his flash can be used to support entering dualist. But its just my personal opinion.