It feels noticeably larger to me, though side by side it's only slightly bigger. Obviously it's not an ergo shape if you care about that. Liftoff distance is a little higher than the KPM with DCU on very low, but still low enough for me. The buttons are a bit harder to click than the hair triggers on the KPM, but not unreasonably stiff. The extra front buttons feel a little mushy after you get past their click point. One kind of cool thing about the extra buttons is that the shape and position makes it pretty easy to learn to hold down LMB while still being able to click the far-left button with the same finger. I find it harder on the right side (I'm right-handed).
I prefer the KPM scroll wheel for scrolling as it's a bit notchier and the travel seems shorter, but I like the Kova's more for use as a button. The Kova one feels a little cheaper, wiggles slightly, and is noisier.
I don't really notice any difference in sensor performance after updating to the latest Kova firmware, but I haven't done any detailed measurements. With my grip (slightly small hands, claw) the sensor placement is a little further forward with the Kova than with the KPM.
I find the extra front buttons really useful and I like the Kova for that reason. If it didn't have them I'd prefer the KPM as it's a little more comfortable for me. But they are both good enough mice in my opinion.