I tried to select an engine for my current project by asking the RCU community. I got a lot of information, but none that I could really use to make a decision with. Here's what I did.

Open up your spreadsheet and enter the following:
Engine
Engine weight
Engine power
Price of engine
Airplane weight
Estimate of fuel type and consumption

Then, calculate:
Total weight of airplane with engine
Power to weight ratio of airplane with engine.
Wing loading of airplane with engine
Performance value (airplane power to weight ratio per dollar)
Operating cost per year.

Once I did all that, I could quickly scan the data and the winner was revealed.