Overall, shallots have a better nutritional profile than onions. On a weight per weight basis, they have more antioxidants, minerals and vitamins than onions. Perhaps the best nutritional bonus of shallots is the diverse content of their antioxidant compounds.
The flavor of a shallot is more delicate, softer, and less abrasive than that of an onion. (Take heed, self-professed onion haters out there.) But the flavor is also a bit deeper, bringing in notes of garlic, which a white or red onion definitely doesn't have.
Shallots make a great addition to stir-fries, sautés, salads, soups, side dishes, and casseroles, and is very often paired with garlic. Combine them with olive oil and balsamic vinegar, as well as fresh herbs like rosemary and thyme to create marinades and sauces for your meat dishes.