Any boat can participate in a regatta. A racing sailboat is one conceived and built for competition. A racer-cruiser constitutes a hybrid between competition and pleasure models.
Centerboarders, monohulls, catamarans and trimarans are all suitable for regattas or ocean races governed by measurement or handicap rules for different classes of craft.
Racing sailboats are all about speed, and speed hates dead weight. Thus, this type of craft does not offer the comfort of a cruising sailboat. Carbon fiber hulls are common and rigging and sails are custom-made of high-tech fabrics. These sails give better performance, but wear out more quickly than cruising sails.
Choice will depend on budget, area of use and crew size. Series model or one-off, it's up to you to select your preferred weapon for confronting other mariners.