I don't profess to being a good gardner, but I do have a short story to tell.
In the past I have failed as a gardner, after having raised beds, irrigation system, yada, yada, yada...I couldn't even grow tomatoes which I categorize as a fruit bearing weed. My corn was looking perfect, and I went out to pick it the next day, and the Raccoons had snatched everything. I was so disgusted that I decided that the farmer's market was the way to go, so I tilled everything under and planted grass.
This last year, Mrs. Engineer decided that she would mix a few plants in with her flower gardens so if they did nothing, there would still be a flower garden. She planted early girl tomatoes, a beefsteak, and a couple of Cherokee Purple heirloom plants that my neighbor (a master gardner) gave to her (the master gardner recently shared that he thought my original garden was to close to a black walnut tree that would severly affect the garden output).
Well I will tell you what, with the few plants that Mrs. Engineer had, we would pick 40-50 tomatoes at a time from the early girl plants...We never got a single decent tomato from the heirloom. I have never enjoyed home grown tomatoes so much as just picking them and eating them like an apple, or pairing with some of our fresh basil and some buffalo mozzarella. Mrs. Engineer was such a rock star in my book, I am really excited about doing some more gardening this year.
I don't know about the disease resistance or weather tolerance of the heirloom tomatoes, but they were within 6 feet of the early girls and received the same love and attention. They simply did not produce. Like I said, I am not a good gardner, but that is my personal experience.
If you want the real low down, shoot ALX a message, he has the most amazing garden that I have ever seen, and knows his stuff.
On Edit: Alx has already jumped in...must have been posting as I was typing too.