I still, sometimes, make chicken and meat stocks the "old fashioned" way, because I've tasted the difference long, slow, simmers make, but if I'm going to use the stock for soup purees, risottos, rices and grains, polentas, or any dish that doesn't rely on that depth of flavor, then without a doubt making stock, in minutes, in my pressure cooker, especially using veggies that would of ended up in the trash, adds not only flavor, but, how could it not add a boost of nutrition too?
The basic difference between the two is visible by the color and gelatinous texture of the long simmering stock, which means much more flavor. I use at least 4-6lbs of bones in a 12qt stockpot that will only yield less than 3 qts of dark rich stock, and I'll simmer it overnight on my gas stove for at least 8 hours. I use these extra rich stocks primarily for my base veg soup, and extra special pasta sauces (for fresh pasta), and dishes I may want that "something special" for. Whereas I can use the bones of one chicken with some scrap veggies and get 3 qts of "light" stock in the PC in less than 30 minutes!
Most recently I've been making asparagus stock using the bits of asparagus you snap off the ends....the parts that are too tough to eat, and pea stock from the discarded pods of fesh peas. With this asparagus stock I've made my risotto, and what else? Soup, of course.....Asparagus and Leek soup. Last year I made corn stock for my squash soups, and to make quinoa and other grains for salads that also had roasted corn in them, but how yummy to make corn chower using it! This year I'll add mushroom stock (you can use the stems which you might normally remove and throw out), shrimp stock....this occured to me as I was peeling them for my risotto last week (I now have a "scrap" shrimp shell collection in my frezzer, lol), and who knows what else! I do know, however, from cookbooks that I've read that cabbage, and anything in the cabbage family, are not good to be made into stocks....FYI.
Life is good, food is joy, and adding beautiful nutritious, homemade stock to your already beautiful, fresh, homemade foods is such a lovely thing.
PS If you're a vegetarian and you do not own, and use, a pressure cooker then you're crazy!