I have the Yamashin and Kajihara and played with the Murata a bit. The Yamashin is thin and good to go out of the box, but the handle is somewhat blah. Wa handles are easy to make/replace though; I am working on another new one for my Yamashin Funy
The Yamashin has a nice profile and is pretty thin as is. The Yamashin has a little more curve to the belly, but works very well on the board.
The Kajihara is slightly shorter (height wise) than the Yamashin, but a hair taller than the Murata IIRC. The Kajihara was a good bit thicker out of the box and benefited from a good thinning and really shines with a full regrind. The profile is similar to the Murata; the majority of the blade is flat and curves up near the tip instead of the continuous curve of the Yamashin. Both work very well on the board, and the shorter height of the Murata/Kajihara doesn't affect performance. The Murata has a very nice grind and handle and is around the same thinness behind the edge as the Yamashin and much thinner than the Murata, but the Yamashin is thinner at the spine throughout on the one I have here. The Murata has a nicer Kasumi finish and is covered in lacquer, which keeps the blade from reacting much other than the very edge until the lacquer has worn off. The lacquered handles are pretty nice, too on the Murata.
So Yamashin is thinner at the spine/overall than the Murata, more belly to the profile, taller, cheaper handle. Murata is around the same thinness behind the edge, better lacquer finish/grind, nicer handle, but flatter and shorter height wise.
Yamashin has the lighter color ferrule, Kajihara has the black ferrule. Murata is similar profile wise to the Kajihara (flatter, less belly), but is a touch shorter height wise than the Kajihara. Both styles work well, but for some reason I like the Yamashin Funy profile better, even though I usually prefer knives with less belly. Go figure!
Both steels take and hold an edge nicely. The Murata Blue #1 will probably hold an edge longer than White #1, but most people sharpen before they need to resharpen anyway and the differences will be fairly minor. It will depend on the board you use, what you cut, the edge refinement, etc. I would say get whichever blade profile appeals to you more and then worry about the handle!