I have no experience with the 572, but I own a 500i and run a later model 462R at work.
The 462 is an alright saw, IDK if it lives up to the hype that some people give it. The light weight is impressive and I do like the air filtration on it. That being said, I've been ruined by running ported 75cc+ saws, so the torque isn't that impressive to me. I also prefer my ported 400 to it, similar power and even less weight.
The 500i is a great saw IMO. Really strong runner, almost feels like a ported saw...especially strong for the weight. Air filtration sucks, some of the other Stihls and virtually all Huskies kill it in this regard. That being said, the rest of the saw is so brilliant, I can overlook the air filter to a certain extent.