I'll throw in my .02 on this.
I've been a weekend detailer for over 20 years now, and I've used a Porter-Cable 7424 for the last 13 years. It's likely the best money I will EVER spend in my life, as it cost me a grand total of $89 shipped back in the day, and I've used it on likely 1,000 cars since then. When it was new on the market, the 7424 was truly a game-changer. If you are familiar with any of the Porter-Cable line, you know they make some great tools.
Having said that, last year, I bought a Flex XC3401 polisher. It was A LOT more money than the 7424, but it delivers results faster than the 7424 would struggle to accomplish. If you're serious about your detailing game -- even if it is only on your own personal cars -- it's well worth the investment. You won't regret it.