Although I've never used push ads, I've been using search ads, however, from what I've been hearing, the good push ads networks are push house (push dot house) and propeller ads. If possible, do let the community know for what kind of promotion(s) (verticals) are you deciding to use push ads, because push ads may not work well for all verticals. Kindly do a thorough research before you finally make any decisions. Seek more clarifications if needed, because you'll be able to aggregate from the suggestions of various members here, which would enable you to take better decisions.