Bearing in mind, for the consumer, more than one option is a good thing for multiple reasons (price and schedule being two of the biggies). So AMS, CDG etc keeps CX "honest".
For the consumer (who is already well looked after) or the loyal QFF member? MH's presence in oneworld won't necessarily keep CX "honest", in the same way that TG doesn't necessarily keep SQ "honest" in star.