A comment on the 3% HP thing: that % number applies for peak HP only, and does not tell the whole story. Higher compression ratio translates directly to higher compression pressures, which drives torque. Higher CR gives higher torque values and at lower RPM's, and thus helps to extend the lower usable RPM range. If you are revving all the time, no big benefit. If you are driving on the street, then the added torque down low is a major benefit.
And higher CR tends to drive better cylinder clearing of spent gasses and thus better cylinder filling. This is always ignored in the 3% statements, which is just looking at thermodynamic power extraction, and totally ignoring other torque/power producing factors. So it is not presenting a complete picture by any means.
