Patrick, Japanese chisels are easy to sharpen, especially if they are made of plain carbon steel (white 1 or 2) and frankly I find blue steel fairly easy to sharpen as well. There are a few forces in effect here which will drive the decision making.
I prefer to work plain carbon steel, it can make a very keen edge, it wears very evenly so you wont notice the cut quality falling apart rapidly. Plain carbon, even when made very hard, can sharpen up on natural stones. Natural stones are quite nice to use, both western and eastern varieties.
I dont think Japanese chisels are the only way, but they're certainly the way I prefer. I like my chisels to be very sharp and I touch them up regularly so I dont need a super wear resistant steel.