Gauge is a regional thing but as CR888 mentioned above .063" is definitely the toughest across all hand held saw applications.
In Australia Stihl saws in .325" and up all come with .063" and Huskies come with .058" up to about 28" then .063" from 32" up (or thereabouts).
I have converted all of my larger saws including Huskies/Dolmars to .063" where I can. .050" simply
doesn't hold up under tough hardwood conditions and .063" definitely transfers more oil to the chain.
Ive used equal parts .050" and .063" and the only chains I've ever had bust through the drivelink were .050" - .063" is far more heavy duty.
Regardless of chain gauge I've always run my oilers flat out with the exception of the 3120XP's on short bars as they resemble the Exxon Valdez crude oil spill if you wind those things up
Remember though that
in Australia our Eucalypt and other hardwoods is completely different to northern hemisphere hardwoods.