Being a member of the nightshade family the tomato produces alkoids and other chemical defenses which are often experienced as bitter in taste. Careful selection in many of our food crops have eliminated many of these bitter substances, albeit that a small amount of these chemicals often are instrumental in their taste. In the tomato a specific class of molecules probably contributed to its success.
Tomatoes are rich in savory aminoacids, the most important of which is glutamic acid, the active part of MSG. The combination of acidity, sweetness and glutamic acid probably gave the tomato its popularity as a vegetable and can also explain why it works so well in sauces, with meat, and without meat. The tomato also contains aromas that remind us of tropical fruits which consist of complex sulfur compounds.
The anatomy of the tomato also has an influence on the taste because the different compartments of the fruit contain different taste elements. A cherry tomato will therefore taste different than a large beefstake tomato. In contrast to cherry tomatoes beefsteak tomatoes contain mostly the flesh and hardly any seeds and pulp. The flesh contains relatively more sugars and the lack of pulp means they have less acid. Beefsteaks are therefore often experienced as sweeter. The seeds themselves can be bitter also facilitating the sweet experience of the beefsteak in comparison to the cherry tomato. On the other hand the pulp in the cherry tomato not only contains acids, it also has a higher glutamate content than the flesh. This can make the cherry tomato so tasty. All these qualities also mean beefsteaks are better for cooking and sauces. Cherry tomatoes can have too many bitter flavour components and have relatively more seeds and skin, which isn’t always pleasant in a sauce.