I've owned both kitaeji and kasumi knives and found that the kitaeji was a bit less reactive than the kasumi. Other than that, I agree with YG420 - there is no difference in performance. Mine had custom handles so I can't comment on the relative size of the stock handles.
The cladding on the kasumi is a single layer of soft iron, though it may contain forging artifacts or clouds that can be revealed by judicious polishing. The kitaeji is made of multiple layers that are not etched, but polished to produce the contrast between the differing metals. So it's more than just polishing differences between the two variants - it's construction differences.