Taste, size, appearance, meaty composition, production numbers and ease of growing. Over lots of years, I'v tried others but about 12-15 years ago I decided Big Boy tomatoes gave us everything we wanted. I love tomatoes in salads (especially those featuring tomatoes), salsa, on tomato burgers (had them off the grill tonight), in chilli and - of course - in BLT's.
I can take a softball sized BB .... remove its skin, quarter it, remove its seeds and enjoy tomato "meats" chilled with Italian dressing with a sandwich at lunch or with dinner. we don't make juice or can them so I have lots of fun giving them to folks who love them and don't grow them. Hope this answer is sufficient. :-)