Thanks for your thoughtful and detailed reply. I pulled the trigger on the 210 Kagekiyo today. I think the size will suit me and I recently filled the 240 position with a Yoshikane that I'm super happy with. The question now is, will I give up either of my 2 current 210s, I should, but I don't know. The Shiki has become my wife's go-to and the Masakage, well I just have a soft spot for...Aesthetically its beautiful. It could be improved with a little more height to it. As far as cutting goes, its enjoyable for tip work. I don't think it does push cuts quite as well as my tsubaya tanaka gyuto, which is the same black smith/steel and wide bevel ground. If I had to have 1 tanaka blue 1, I'd advise going with a more traditional gyuto, but its a fun niche knife to have and again aesthetically cool.
Between it and the Hitohira, I'm going to say some possibly controversial things.
1) I believe that these knives, along at least with the hitohiras and the tsubaya Y. Tanaka knives do have variation in their dimensions. That's not to say they aren't typically finished very well. But for example, my dad and I bought the Tsubaya knives at the same time and when we opened our boxes back in the states, his was much more stout and taller than mine. The CKC knife I examined in their store a few years back was also a little bigger than the one I got in the mail. Again they both have strengths and weakenesses and none of them are bad knives or finished just different. I get the impression the hitohiras are the same way. Bottom line, there's a potential to have a little variation between the same knife in these lines.
2) None of these three knife brands are that different within the standard bounds of variation as far as the actual pathway of the blade profile and cross geometry wise. You may get a taller one, you may get a wider one etc.
So in reality, its up to you what sort of aesthetic and bells and whistles you like. The magnetic in a kagekiyo saya is cool. The lacquer handle through me off when I first saw it (I had thought all sides had lacquer) but its grown on me a lot and stands out in a traditional but different way from my list of buffalo horn/ wood handles.
One other thing, is that both lines are undersized. So be aware of that. My sweet spot is a oversized 210, undersized 240 I think. If you're used to a bigger 210, you might want to consider a 240.