I have always ran 3/8 on all my saws without any problems , never had a need to go up to 404 yet..I would stick to the 3/8 chain..but what are you cutting ?
I use .404, it takes a bigger chip of wood with each bite. Also it's stronger and won't stretch as much as 3/8". It takes a little more power to pull, but I believe you get more work done with it. 24" or longer bars get .404 on all my saws. Usually full skip for lack of so many teeth to sharpen. Just my opinion. Have a great day!
I always run a 3/8 full skip on my 660 stihl. I've tried the 404 and wasnt real impressed. You will get more speed, which means faster cutting (more money) with the 3/8 and its less stress on the saw. I run it everyday with a 36in bar and it works great...just my opinion though