This is an interesting point that you make. It's aggravating too, because I realize myself that I do this in certain cases.
heirloom tomatoes do taste better, they are what a tomato tasted like before they were altered to make them last during transit; same as heirloom pork is what pig tasted like before it was bred to be leaner. the idea of convenience over flavour really took off in the last 40- 50 years but fortunately things are turning around a little. as well as flavour the look of heirlooms is way more appealing. as for using them in a restaurant, if you change your menu seasonally you can take advantage of them for their flavour, coulour, and appearance. used raw almost everyone will notice but cooked it might not be worth the extra cost unless you use one of the different coloured varieties. i hope that the big growers don't start marketing mass produced tomatoes shaped like heirlooms.
I look at it a little differently, good heirloom tomatoes (or many other food products) taste better than many of the current varieties, but there are numerous heirloom (read old, out of favor) varieties that do not taste good at all!
Now, if one defines heirloom to mean good tasting varieties that are difficult to find in commercial markets, then I'll concur.
I sort of remember reading an article in one of my cooking magazines some time ago. This fellow in France took over his family vineyard and over the course of a few years gave up the grapes and went with tomatoes. He grows something like 525, maybe 550, don't recall the exact number of different varieties, some of which he brought back from near extinction. Wow. I do my three types a season, I can't imagine dealing with 500+ types!
Here's a bit of specific info about heirlooms which may or may not be relevant to you (depending on where you live.) Here in western N.C. there are a LOT of small farms growing these tomatoes now and they don't charge much for them either so you get to taste a lot of them. A couple of examples:
German Stripey: Yellow with red and orange stripes, inside and out. Can be really misshapen but incredibly good. Very low acid. They look great in a salad, too.
Pink Brandywine: This one came out of Amish country. Dark red/pink. More acidic than the Stripey. Close to being the perfect tomato IMHO.
Cherokee Purple: When these are ripe they really are close to purple. More sweet than acidic.
Mortgage Lifter: I love the name of this one. People planted these because of the yield per plant. These suckers can get up to 3 pounds. Very close to a beefsteak but there's more happening in the flavor. You'd have to compare them to see what I mean. They're kind of a flat shape which means that a single slice can cover a whole piece of bread.
Persimmon: This is one gorgeous tomato. Pink orange like a persimmon. Meaty rather than really juicy with a really fruity taste. Almost an apple flavor to it.
Aunt Ruby's German Green. This one stays green when it's ripe. It's got a tang to it, almost citrusy. Great to use in place of those green/red tomatoes you get in Italy for salads. Also, it's cool to have an all green salad with tomatoes in it.
This can go on and on. If you love tomatoes you can really get knocked out by some of these. That's not to say there's anything wrong with a perfectly grown beefsteak from Jersey. Main thing is you can't get good ones in either supermarkets or from regular suppliers. And, of course, the farther you get away from big cities, the cheaper and more plentiful these things get.
If you want to see a great list with some pix and descriptions check this out: http://www.appalachianseeds.com/tomato-plants/tomato-plant-catalog
I love tomato season. We eat them every day for breakfast. I weep when the season is over.
It won't be long now before the Wasatch Community Gardens tomato sandwich party. It usually involves about 20 - 30 different varieties. And what I taste there usually determines which varieties I grow next year. I'm kind of bummed, I still don't have any fruit on my white giant plant. But the growing season isn't over yet.
I tried pink brandywine last year, another really late bloomer. But I really liked all the purple gypsies I had early on!
I grow all heirloom tomatoes, mainly because you can save seed and are not dependent upon the giant seed companies to grow your plants. (I grow most everything from heirloom seeds). I've had some really unique tastes, but mostly settle upon the ones that the really good hybrids were created from. I do enjoy seeing a plate full of multi colored tomatoes, though. So pretty