I lived at Niseko for a couple of seasons, so I can say that you are going to love it, but the weather is not often good. Hirafu is my favorite, but Higashiyama kicks as well. The pensions are the way I usually go in Japanese ski resorts as the master often skis with you- nice touch.
P.S. Save some energy for night skiing- it offers the nicest weather and you can see fox occasionally. Let me know if you need specifics...