:welcome:
What are you going to be using it on? Your personal vehicle(s) or are you using it for a detail business? If you're correcting paint and time is a major factor, then go with the Flex.
I recently purchased a Flex and love it and I own a DA as well. With the LC changeable backing plate system, I can quickly switch from 5 inch pads to 4 inch pads without changing plates. I like the forced rotation, especially in tight areas where my DA tends to stop rotating.
Bang for the buck kinda' depends on what you'll be using it for. For a daily driver, can you justify the initial expense of the Flex, though? Only you can answer that question.