I've done trips with both mike ball, and kangaroo explorer (cairns dive centre). Totally different trips!
Mike ball was about three times the price, but substantially better dive sites, and better food.
Kangaroo explorer was a much younger croud, mainly young backpackers. I actually preferred kangaroo explorer, because I was 22 when I did that.
Horses for courses though - do you want a bit more luxury, with more focus on teh diving itself with a demographic of mainly US, japanese and euro 35-60 year olds, or do you want more of a party type atmosphere, with the 20-25 year bracket backpackers?
Horses for courses, both are good at what they do, but totally different trips.