A 0.2:1 compression inrease alone isn't going to pick up 10 horsepower... tuning and fuel curves most likely have more to do with the power difference than a measly two tenths of compression.
As for your question, the general rule that people go by is typically 4-5% more power per FULL point of compression increased. 0.3% might get you a whole whopping 1% of power. It's not worth swapping your pistons just to change 0.3%, unless you want to change from cast to forged or something like that.