I think there’s also a variety factor, heirlooms are usually very unique and fun-looking. But yes I think taste is generally good too. I’m growing heirloom Zucchini and Tomatoes this year. The tomato flavor certainly isn’t bad, about on par with other good garden tomatoes. The zucchini on the other hand is out of this world good, and retains the flavor even when the fruits are large, unusual for most other Zuccs. (Variety is Costata Romanesco)