I thought I'll add my 2 cents to this thread. I recently got back from an epic snowboarding trip in Japan. I went to Hakuba, Shiga Kogen and Niseko.
Hakuba - I really can't remember much of Hakuba being the first mountain I went to while in Japan. I remember it being not as touristy as Niseko. The mountain itself, I really don't remember much. Being start of the season, there was not much soft snow around. The scenery though is awesome! Love the local town atmosphere.
Shiga Kogen - I only spent a day trip there. The runs I was on were nicely groomed, beginner runs. I would say this is better than hakuba in terms of runs. I loved the atmosphere of the place. There was basically no tourists, so everyone was a local japanese boarder or skier. Being a boarder, there were some runs which would suit more skiiers, they were flat or had moguls. I would recommend staying at a ryokan (traditional japanese hotel) for at least one night if you going to Shiga Kogen. Onsens will do wonders! Also the Onsen Snow monkeys!
Niseko - By far the best conditions I've ever ridden in. On the famous strawberry fields run, I was in a good waist deep in powder at times. Falling was like falling in pillows, amazing. When it comes night time, it was ridiculous. Best night boarding EVER! There is a large number of runs while night boarding. Also I've never seen so much snow in my life. It was almost constantly snowing there. On the base of the mountain, 10-15cm of fresh would fall while night boarding, this meant you could even ride your board down the street (which is prohibited). They had a good setup for people that like to ride park, (heaps of rails, tables) or guys that love the big jumps.
The place is overrun with aussies. You can take this as a bad or a good thing depending what you wanted to do. I am aussie myself but it didn't feel like a holiday almost because basically everyone was aussie. The nightlife there is great with huge number or bars to go to. I never got to have a drink at any bars though but I assume it be over run with rowdy drunk aussies though. So in terms of total package, Niseko is definitely the place to be.
In reference to someone saying its hard to get by without knowing any japanese is wrong. You can get by in Japan without knowing any japanese. Most signage will be in english also most people have basic english skills so communicating is not that hard.