I use Rose (OSB) boxes, or more correctly National brood boxes cut down to Rose box depth, an easy mod. You are correct frames and boxes (i don't use the dedicated Rose box) are a bit more expensive, about 10% more but there are advantages. Thornes sell the frames & foundation, so readily available. You only have one size of kit, everything is interchangeble, less to carry to the out apiary. I find I buy less kit as I don't have to have two lots of spares in different sizes. Manipulations are easier being able to swap frames from supers to brood area & visa versa. Weight is a bit more but not been a problem, I would not be able to lift a National brood box full of honey. Buying bees in nukes is a bit tricky but they go into a national brood and transition to Rose boxes over the season. That said I've only every had to buy one nuke. On the whole I have used both Brood + Supers and Rose Boxes. I find OSB much easier and convenient.