In my opinion I don't think that hybrids are 'better' than heirlooms, or vice versa (except in the matter of taste, when it comes to certain veggies. My tomatoes and my zucchini are heirlooms because they taste SO MUCH BETTER, for example ).
They both have their pros and their cons. I suspect it all boils down to what you want out of your garden and what's most important to you. If you live in a disease infested area, you may want a disease-resistant hybrid. Similarly, if you live in a hot climate, a hybrid tomato bred to do well in heat might be a wise choice.
On the other hand, if you're like me and you absolutely cannot stand the soul-less, tasteless, frankenseed nature (not to mention chemical-laden and dubious nutritional quality) of most everyday, ordinary grocery store produce, heirlooms (even though they are tougher to grow and less prolific, in general, though we can hardly keep up with the heirloom zucchini . . .) would be a better choice for you.
Other factors may be the time you have to spend on a garden, how much sun you get, whether or not you garden in containers (in my experience heirloom veggies tend to sprawl more than their hybrid counterparts!), and whether or not you want to save seeds.
In the end, I'd suggest doing your homework and figuring out what's most important to you and going from there.
The primary motivator for me in making my garden mostly heirloom is that I wanted to get back to REAL food, food that hasn't had all the nutrition and character and stuff bred out of it. I wanted a tomato that looks and tastes and feels like a tomato -- not a red tennis ball. I wanted a strawberry that was juicy and flavorful and looks and acts like a *strawberry*, not a crunchy, woody, sugar-sweet strawberry-shaped piece of candy.
So, I'm growing my own. Yes, I am *that* dissatisfied with what my grocery store can give me. I wanted other options -- but the only way to get what I wanted was to do it myself.
So far, suits me just fine
Whitewater (YMMV, of course!)