I've never held a kihon, but it looks to be more of a practical design. The Kwaiken is really cool, but personally I've found it to be just that, and best for a gentleman's carry (if even that). My kwaiken had a working edge out of the box, wasn't razor sharp. Blade stock is a bit thicker and I could see heavy use creating hotspots since the handle is so thin. Otherwise, it's a snazzy looking knife, it's hard to beat that slim design. The flipper action isn't the best though.
I would think if he's going to use it for work, get the Kihon. And if it's just a nice gift that he can use to cut here and there, get the kwaiken.