I know ASICMiner won't sell equipment until BFL releases theirs. At that point, they will collude through pricing to form a duopoly until a third company provides equipment. I think BFL will have a slight advantage in timing to get to market. I think they have more expertise in selling, and shiping, as well as quality control in place. ASICMiner will essentially be the AMD to BFL's Intel.
source?
ASICMiner has said that they will be self mining to recoup costs with first batches. They will have no real incentive to release products until they run out of space to mine, or they start to make more money selling than expanding mining. BFL releasing their product will kill ASICMiner's profits from mining.