It's a good lateral move from a 440. A 400 is pretty sparky too but I think he'd be happier with a 462.
I love my 67cc Stihl MS400. Pro model thats been out a couple years. (i bought it used with a couple extra aftermarket accessories that enhance performance) With a 20" bar it cuts a lot of my "bigger" logs. It can easily handle a 25" if needed but i have bigger saws for that. The MS462 is a few ounces heavier (powerhead wight) for a couple extra $200 or so. The MS362 is a good option for the 60cc class. I own a 361 which is the precursor to it. These saws come mtronic which a computer chip controls the carb or with a manually adjustable version.
Love my 400! But I think 462 is more of a direct replacement for the 440. A 500 would replace both the 440 and his 660 and use all the same bars. But those are thirsty and a 572 or 592 husky are going to be smooth and have plenty of power too. Nice saws if you happen get a “Wednesday” saw. A couple porters have pointed out plenty of QC issues with the 5 series Huskies. Good dealer support is important either way.
I had to check. The 440 is 6.3kg and the 500 is 6.2kg. Powerhead weight only so its actually lighter.
I'm gonna break the line and suggest a 372xp. It'll look nice next to that 346 & 350. Can get one of those and stuff-it for less than a 500. Secondary would be a 7900. 80cc powa, 70cc weight.
Sorry for leaving everyone hanging. My FIL cancer came back and obviously a new saw is the last thing on my mind.