I think we need more details on your tournaments before giving an educated answer. What are the races to?
What are the handicaps?
Besides those two things....it is easier for lower skill level players to run out in 8ball. Reason for this; they don't have to play precise position on any ball..for example=.miss position on the 13 and you can shoot the 11.
Most good players don't mind giving 2/3 games on the wire going to 7 in 9 ball but in 8 ball it becomes a lil tougher.
Whatever BCA rules/races for amateurs are is what the tour uses. And if it matters, they only play on 9 footers.