Should beef jerky be cut with or across the grain?
For me it very much depends on what meat I am making jerky out of.

With the grain is much more solid than against. Just as you might expect.

If you are using relatively tender meat then cutting across the grain will result in a batch of jerky crumbs. Cutting with the grain will be good.

If you are using very tough meat then cutting with the grain will be absolutely impossible to chew.

I often make jerky out of brisket which is very tough. I compromise and cut at a 45deg angle. This results in very tough, jerky but it separates into smaller, more manageable chunks when it is chewed.