Both skis are sick and very versatile.
You can have fun on the Opus no matter what the conditions are. The opus is a ski you would like better than the Pettitor in heavy crud, spring slush, and hard pack snow. Ski is a beast!
The Pettitor is going to feel quite a bit damper, not as damp as the current year or 10/11 ObSethed. Pettitor will get bounced around a bit more in the crud, slush, and won't grip as well on the hardpack as the Opus. If you're a lighter weight guy and want something that is really agile in the tighter trees, bumps, chutes etc... Petittor would be a better option because it's softer and lighter.