Judging by wafflepool's stats page, it seems the btc/MH/day is about 0.011, whereas at MC I was getting used to 0.013 atleast. I hope to see wafflepool's income increase as more power is added.
More power will decrease profitability not increase it. We will drive up the difficulty of the coins we mine, driving down their profitability. Pooled mining is not a "contest" where the idea is for your team/pool is to be bigger than the other team/pool.
There a lot of randomness, and more power can help with that. But it isn't clear whether a profitability gap (if one exists) is a random factor or algorithmic differences in either mining or trading. If the latter than growing the pool won't help, only improving it.