Don't forget that the internal resistance is going to be different for the different sizes of cell too. You'll get higher C from a smaller cell than you will a bigger one, CALB reflects this in their spec sheets too for the maximum current ratings.
I think ThunderSky/Winston is the only company using Yttrium, I'm not convinced that it means all that much though.
It seems we may be behind on testing, previously testing showed Sky Energy/CALB being on top for internal resistance, discharge performance, and Ah tested per Ah rated. Updated testing may be in order but I think both of these two companies are improving as time goes on.
Either way, don't look too much into specsheets, ThunderSky for example have always had discharge charts that don't seem to match their actual performance when tested. Not to say they don't perform well though, just not quite what they show.
"Now it appears they are ahead of the pack" Neither of the three discount LiFePO4 manufacturers are ahead of the pack. Headway, A123, SAFT seem to be ahead by quite a bit more. I think that the newest Hi Power cells may be much better than they once were now that they have released their higher power cells. We really need fresh testing but I think that people will be happy with any of these six. ...well, SAFT doesn't count, they aren't available and neither are the A123 cells as far as I'm concerned for an EV.