The SL is ordinary in powder due to the stubby nose it has. I took mine to japan and it sucked badly, waste of baggage weight.
Like I said (maybe with the wrong emphasis). The SL floats ok in powder - but I haven't ridden any twinish board that does a great job at floating in powder compared to a dedicated powder board like the Burton Fish, Prior Khyber (similar in shape to Malolo), or the Never Summer Summit.
Update what did you mean by stubby nose? I have a 2009 SL and it has a standard nose, which is stubby compared to say big-nose powder board, but it isn't as short as the blunt-tips on say the Proto (I have a 2012 Proto).
However, these park-only kids (it's not like I'm not going to park a lot myself) don't know any better - and there are often at crappy little resorts... not like your Hokkaido.
Back to what board for OP to get:
If you want something more than just ok in powder... Maybe the Pow Stick or Sick Sick (I heard those was a twinish powder freestyle board). However those boards sound kind of crappy for freeriding (to be honest... the Burton Fish was really crappy for freeriding too, the Prior Khyber is so-so, the Summit is ok). I haven't ridden themself and so I can't comment much about them. I saw the title said "Never Summer SL" and I tried to share my experiences with that board to help other people decide.
Nivek is suggested a K2 Happy Hour (maybe that?)