The Breville Smart Oven Air Fryer (BOV860) and the Smart Oven Air Fryer Pro (BOV900BSS) look similar in photos, but the Pro is meaningfully bigger and meaningfully more capable. If you're trying to choose between them, the differences fall into four categories: size, cooking functions, hardware, and price.
Interior capacity. The Pro has a 1 cubic foot interior; the non-Pro is closer to 0.8 cubic feet. The Pro fits 9 slices of toast, a 14-pound turkey, and a 13-inch pizza. The non-Pro fits 6 slices of toast, a 12-pound turkey, and a 12-inch pizza. If you cook for more than two people, that extra capacity is the single biggest reason to step up.
Cooking functions. The Pro has 13 preset functions: Toast, Bagel, Bake, Roast, Broil, Pizza, Cookies, Reheat, Warm, Slow Cook, Air Fry, Dehydrate, and Proof. The non-Pro has 13 listed functions on newer revisions but historically shipped with 11; the practical difference is that the Pro's Slow Cook can run a full 12 hours and the Pro adds a dedicated Proof setting for bread dough.
Heating hardware. Both ovens use Breville's Element IQ system, which controls the heating elements independently to direct heat where the food needs