Statuario has a bright white background with cool grey veining. Calacatta has a warmer, creamy background with gold, honey and grey veining.
Because Statuario is cooler and more graphic, it suits contemporary interiors, lobbies and modern feature walls. Calacatta's warmth suits classic bathrooms, kitchen islands and spaces with brass or wood detailing.
Practical note: Calacatta is generally more expensive because good gold-veined blocks are rarer. If your budget is tight, Statuario gives a similar luxury impact at a lower price.
Whichever you choose, buy enough from one batch. Marble is a natural material — a second order six months later will not match.