All or none can prevent you from getting shares in the first place. Personally I roll with it off as my buys aren't usually big enough to take out the whole bid or ask on one PPS step. I.E Like a 500$ buy on PDXP is only like 40k shares right now but if I were using 3k$ it would be in the hundreds of thousands of shares making it harder to get all one price. All or none can be beneficially as you can get better prices than you even originally are asking for.