Depends on what you need and how tight you are for points. The Burna Bommer is great against troops and the fact that it's rokkits will hit somewhere is a plus with typical Orky accuracy. However, a kitted out one is 190 points IIRC. The Blitza Bommer is one of the better anti armor things Orks have. And it's rather cheap points wise. But is does have a tendency to crash into things rather than just bombing them. But any true Ork player should embrace the chance to accidentally blow themselves up as long as it's loud.