You seem to be stating you see a difference in profits when you place buy and sell orders yourself rather than a pool which would sell the coins as they are mined then buy the alternate currency. If you are psychic and can predict what orders will be filled at various price levels in the future then there really is no need to mine coins at all, just profitably trade.
Pools are going to trade at the current buy price, lowering it with each sale. You're better off listing in between buy/sell if you want to maximize profit without dumping the price. But that's really irrelevant here.
When you use a profit switching pool, it's going to charge more in fees. On top of this, you have zero transparency. They could be paying you 70% of what you should be getting and you'll never know because you have no idea how many coins were mined and how many should have been. There have been pools in the past (at least in 2013) that went out of their way to obfuscate earnings to screw over miners. So not only are you paying increased fees, you're also risking more loss.