Mega Superstar Pack vs. Premium Superstar Pack

Under the Loot tab, there are several options...among them is Mega Superstars and another is Premium Superstars. I understand the Mega Superstar pack can get you the 3-star guy, but it seems if you miss the 3-star guy you always get junk. Are there better odds with the Premium Superstar packs for guys I don't already have? Which do you guys purchase after you get up to 400 dollars in game?