I have a Stihl 076 with .404 chain and am looking for the right file to use. I have been working with 7/32 but I also found 1/4“ and am not sure which is best.
They both work and best depends on what you're cutting with it.
The smaller one gives more hook and cuts faster, the bigger one less hook and is more durable. Fine tune your filing to suit your needs.
As above... also check what the manufacturer recommends for that particular chain. On some chains it works well to start with 1/4 & switch to 7/32 when the cutters have been filed down a bit