In my experience, shiro kashi does splinter, especially if you're as ham-fisted as we are. This happened with a couple of Iwama-style bokuto, even though we were quite conscientious with the application of tung oil. It is a better material than red oak for contact work though, and with a bit of sanding and reapplication of tung oil, the shiro kashi remains serviceable.
I'm using a pair of hickory bokuto that have received a severe dosing of tung oil. They will dent more, and are lighter than shiro kashi weapons, but so far they have never splintered. I figure tung oil impregnated/stabilized hickory would be hard to beat in terms of price/performance, at least for those of you with access to hickory.