Hi David
I do tend to use both I have the option with the lapping film to also add some courser wet and dry I used some 120 grit to polish the grinding marks out of the sole of the No 80 scraper plane I have just got. I tend to use my Veritas honing guide with the film and the diamond plates for re grinding chisels and plane irons using Paul’s method, After lapping the tools on the diamond plates I may then use a very fine film to finish with. It is handy to have both methods available in the same unit