Gerry is correct... like with most things detailing its not about which is "BETTER" its about which one suits your needs and requirements.
Short Pro/Con list for each off the top of my head.
Powerful and capable of more serious correction
Graduated trigger "throttle" allows for more control
Pistol grip and bale head are comfortable to work with
Clutched startup makes for smooth start/stops
Can be a little fatiguing to work with for long periods of time (shoulder burn!)
Vibrates a fair amount... not as bad as some tools, but not the smoothest tool to work with.
Learning curve to get 'perfect' is slightly steeper thanks to the forced rotation and the wrinkle that adds to the process.
Limited on pad size options even with aftermarket plates.
100% made in the USA
Smoothest operating tool in the business, very low vibration
All metal housing is very durable
All parts are easily serviceable.
Dual 4" heads allow you to get into various spots that larger pads won't fit (pillars, etc)
Can accept various attachments for other tasks besides polishing (coming soon)
Easy to pick up and learn with.
Less powerful than the flex, may require more passes on more damaged finishes.
Takes more time to fluff/brush 2 heads than just 1.
Takes more time to setup for use (attach and center 2 pads each time)
Edited by Dylan@Adams, 05 August 2013 - 05:24 PM.