Good morning everyone. Being a newbie to all of this, I wonder why folks purchase and use several DA polishers. When working on a car as a hobbies, a Craftsman ratchet will work just as well as a Mac, Matco, or Snap-On if they are the same length without one being longer or shorter than another. If you have two or three DA Polishers that are all free spinning models, all have a five inch backing plate, all have speed adjustments, etc, why are three different models needed? Lets say for example that you own a Porter Cable 7424XP that you have owned for a few years and it still is mechanically fine, why would you upgrade to a Flex or Rupes machine? These are newbie questions and I am trying to learn. Thank you for the help.