Daniel,
REAL power to weight doesn't matter much, and doesn't necessarily give you an indication of 3D performance. THRUST to weight will give you a much better indication.

Example using a thrust and horse power calculator with the same pitch prop to keep it fair.

a four stroke turning a 16x6 at 9000 rpm results in 1.72hp

a two stroke turning a 12x 6 at 13800 rpm results in 2.33 hp

Despite having having significantly less horse power, The four stroke turning a 16 x 6 will give you almost 2 lbs more thrust. You will be able to hover a heaver airplane and have better pull out even though you have less horse power.