Good question! In my experience, changing paper grades tends to have a more pronounced effect on 'local contrast' than does altering development times. (I haven't a clue as to why.)(posted 8515 days ago)For example, if you have a high contrast image on film and have to use, say, a grade 1 or grade 0 paper, the mid tones on the print will tend to become muddy and quite unsatisfactory due to the lowering of local contrast. On the other hand, reducing development time to, say, N-, will permit the use of a normal (grade 2-2 1/2) paper grade and far better mid-tones. On the other hand, I find that, for low contrast film images, increasing paper grades to,say, 3 or 4 tends increase local contrast and that, for many subjects, the increased local contrast produces a 'punchier' image which may prove to be quite satisfactory. (Of course, you might not want to do this for a portrait of a lady friend where the increased local contrast of facial skin tones may not be exactly pleasing to your subject. )
Hope this helps.