SO you've ran them both side by side? Im NOT trying to stir crap up, just asking? For ME, weight is 2nd, cutting ability is 1st, and at less than 14lbs powerhead weight, I aint found ANYTHING that will cut with a 500i. A 390xp wont do it and its got several POUNDS of weight advantage over the 500i. If you've read any of my posts, you will see that Ive always been a Husqvarna user simply because pound for pound they would out cut anything stihl made. I also said thatif stihl ever came out with a saw that would beat them pound for pound, I would buy it. Well that's exactly where I am.
ETA: you aren't the only one around here that cuts BIG oak either, I cut trees sometimes that will average over 2k ft per tree and the stihl has more torque and chain speed than a 390xp even in that size wood.