The whole issue of which brand is better should never be anything more than a little good natured ribbing. Unfortunately, due to human nature, it usually devolves quick, fast, and in a hurry. I've made a handful of brand comments here and there, not out of brand loyalty, but just for a chuckle. In my opinion, that's all they should be for. Not much more I can say on it.
The OP stated stated that the 572 and 500i are the ONLY two saws he is interested in. If anyone wants to debate other saws, start your own thread on the subject.
@woodfarmer, you stated that you want a powerful yet lightweight saw. On paper the 500i wins on both accounts:
500i - 6.8hp, 13.7lbs
572xp - 5.8hp, 14.5lbs
If price is a non-issue, go with the 500i based on only the two criteria you've listed so far. What's the next thing on your priority list or thing that you like about your other saws? We can TRY to talk about individual characteristics and get you help in your decision.
Or if you JUST want to know what other peeps will do, not necessarily why, make a poll.