From my understanding(VERY limited, take with grain of salt) the chrome sticks to the barrel better. I don't know that a thicker chrome lining does anything...really. When chrome wears down it can chip which would be a worse harm to the gun if it was thicker. Perhaps the thickness keeps it from chipping as easily.
Now, onto the "how is it better, ect."
Well, the proponents of CHF say the gun is more accurate because it has less flex and malformation when extreme heat is applied. IE: fully auto fire theoretically holds point of impact better on a CHF barrel. This same resilience can theoretically account for longer barrel life.
You are shooting on chrome either way, so accuracy is and always will be barrel to barrel, button or chf, imho. However, accuracy is also measured by how well a barrel holds point of impact so if there is truth to the heat theory then the barrels could technically be "more accurate" under certain high stress conditions.
That said, there aren't a lot of studies or facts on the actual benefits of CHF over button rifling or vice versa. There are however, many anecdotal and marketing materials as well as facts about how said processes are done. Perhaps a metallurgist can chime in.
Edited: Read the post below mine