I suggest looking at some mountaineering backpacks in addition to (if not in place of) the Burton's and Dakine's.
Most of the winter alpine packs that have ski carry also now include board carry.
Osprey and Black Diamond would be at the top of my list.
IMO you may pay a little more but you will get a serious product with better craftsmanship, materials and features.
Agree with this. I've used osprey packs for years in various outdoor endeavours, and they are super solid packs.
End of summer I picked up a Kode
series in 30l size with a hydration bag too. That series also has a smaller 22l size. They have a few options for snowboards, but I don't recall off hand if they have a horizontal carry.