Underwater Case for S100 OR get a GoPro Hero 3?

I have an S100 that already doesn't get enough use because I also have a DSLR.  I want to do some helmet-cam type stuff this winter of my kids skiing.  Obviously the GoPro Hero springs to mind, but would it be just as effective to simply get the underwater housing for my S100?  the cost is similar, about $200 for the case, or $200 for the basic Hero 3, although I would probably go for the silver edition at $300.

Which would be better?  I would think the lens on the S100 would be better and that it would be nice to have the zoom, but am I missing something?