My understanding is that a densitometer can be used to establish your effective film EI and effects of on highlights of various development times. Taking it to the next level, as Phil Davis does in "Beyond the Zone System", you can tie your film/ developer combination to the appropriate photographic paper.

Much the same results can be arrived at experientially For example, if I find I want more shadow detail in contrasty situations I lower my EI. I normally rate Tri-x at 160. I also cheat a bit when I develop sheet film...I take two exposures of each subject and develop one sheet for 6min and the second for 8min-then print the one I like the best.
I have no doubt that taking a systematic approach to testing would provide a firmer basis for your work, for the evaluation of new materials, etc., but I also believe it's unnessary.

I believe its much more important to pick a paper that works well with your film and developer combination. This can certainly be done with a densitometer, but it can also be done visually.