Heirlooms usually have much better flavor. They don’t ship as well and and sometimes are less disease resistant so big growers will go with the hybrids. But for a personal garden they are the way to go.
I spend more effort improving my soil than anything else. Makes for much stronger plants.
I live on the high ground within a few 100 feet of a river, which flooded a few weeks ago leaving lots of muck and silt when the water receded. As soon as the trail dried, I went down in my 4x4 and gathered a couple of buckets of the stuff, brought it back and put it on my tomato, Serrano and zucchini plants-I noticed over the weekend that the plants have triple the number of blossoms they did before, and the tomatoes are setting 6 and more fruits at a time. I don’t know if it was the fish s*** in the river muck, but it certainly didn’t do any harm-I will have tomatoes to eat and enough to barter along with my fresh herbs for free range eggs and goat’s cheese from a neighbor...
Certainly true of tomatoes, beans, peas, peppers, chilis ...
I am a transplant to South Carolina and failed miserably at trying to grow gardens with plants suitable to Ohio. An elderly neighbor directed me to heirloom varieties native to the Carolinas. Problem solved.