Gunma has remained relatively off the radar for foreigners compared to the now hugely popular Nagano and Niigata Prefecture resorts like Hakuba, Nozawa Onsen, Myoko, Naeba-Kagura and Shiga Kogen.
So you can still get a lot of powder lines with less competition for them here, especially midweeks. Tenjindeira near Minakami is getting better known, but the Katashina Village area is a bit further off the shinkansen and freeway routes.
Size-wise, Oze-Iwakura is more like Madarao, a smaller area that exploded in popularity thanks to a pro-active tree course and powder policy. If the same happened here a similar effect would likely follow, because there are a decent amount of tree lines and powder courses at gradients up to 40° on the marked runs.