If I am reading this right, it looks like the chainsaw file is smaller in diameter than the #19 bit.

Of the two options, which is better?

I have a reamer but it does take a bit to work it through. To be honest, still kind of surprised that this is still something that needs to be done on version 4 of the buggy.

Lastly, what is the diff between the one referenced and this one:

https://www.amazon.com/Oregon-32-Inc.../dp/B000IC26XE