Re: Your favorite DA?
I want to get a DA for light work on a new car. Which one is "the best"?
There are two classes of dual action polishers discussed here, the Flex 3401 and the Porter Cable style.
Flex 3401
The Flex is in a class of its own and while it's considered by many to the the best dual action polisher on the market it's built like a tank and is somewhat pricey.
Porter Cable style
These are probably more the type your looking for but make no mistake, these are quality machines capable of correcting some of the most stubborn finish defects.
- Porter Cable
- Griot's
- Meguiar's
Porter Cable wrote the book on these polishers long before the other two were even through of.
The first generation
Porter Cable 7424 was available to customers 12 years prior to
Meguiar's announcing they were entering the market with them offering their
G110 polisher in 2006. I'm not sure when Griot's began offering their polisher...
The
Porter Cable 7424 basically set the standard which made many if the features between the 3 interchangeable.
To the best of my knowledge
Porter Cable is the only company listed above that designs and manufactures their power tools. Griot's and Meguiar's are not in the power tool manufacturing business therefore contract their orders and my guess to the lowest bidder.
Griot's has the most powerful motor among the three. The
Porter Cable 7424xp is the second generation polisher which outsells the others combined.
Meguiar's falls into the same realm as
Griot's in regard to manufacturing power tools.
Pad Size
The
Porter Cable style polishes are right at home with a 5" backing plate and using 5 1/2" foam pads, not the 6 1/2 diameter pads typically offered.
Pads & Friction
The size or surface area does not directly affect the frictional force between two surfaces until downward force or pressure is applied. Reducing the pad size will only improve the mechanical efficiency of the machine.
The motor of your polisher produces some amount of power. The larger the pad surface area the harder the motor must work. Now, most will say "it's only 1 extra inch", but when it comes to surface area and friction your really talking about an additional 10 square inches. Now take a look at the difference between the 5 1/2", 6 1/2" and 7" pad...........Size does matter!
- Surface Area - 5 1/2 pad = 23.75 in²
- Surface Area - 6 1/2 pad = 33.18 in²
- Surface Area - 7 pad = 38.484 in²
There is a direct relationship between the pad surface area and the polishers ability to transfer adequate power to the pad improving it's overall performance.
My Choice: The
Porter Cable 7424xp
I have read articles by some of the pro detailers that have stopped using the rotary altogether for correction work, but it still has its place in finishing polishing that a DA still struggles to contend with IMO. 
