I'm a huge fan of chassis dynos. They allow you to for the most part dial in your a/f ratio and at the same time, find out what kind of power you're making across the power band. Some people have criticism for chassis dynos and believe there are too many variables to accurately gauge real power output...and I don't want to entertain that argument here.
What I can say is that chassis dynos are great for tuning and I believe there is enough consistency with dyno brands, like dynojet, to feel confident about the power numbers the dyno reports. Converting these numbers to engine power at the flywheel is just an estimate based on drive train loss, but one could argue that (knowing) what you have at the wheels is the more important number.