It really depends on how you ride. If you are MX racing hard with non-synthetic, go with a mixture in the 40:1 range. I ride trails, sometimes hard, and run full-synthetic Motorex and use 50:1. The manual says I can run up to 60:1 for trail riding. With modern Synthetics 32:1 is old news.
For the mixture vs power debate. I would think since less oil = more gas, and more gas = more power, then less oil = more power. This may just be made up for in the required re-jetting though.