28 mm is minimal width if you don't want to run very high pressures. Easier to pump tires with a cheaper pump if you need to fix a flat on the road. Also quite more comfortable than 23 and even 25 (if the same tyre model is compared).

32 is a bit more comfortable, but not good enough for bad pavement, especially if hauling something on the rear.

37 is the minimal width for poor quality roads, or for hauling groceries and a child seat back. Going wider than that has minimal comfort gains, but often hard to squeeze under fenders.