Really really good. My one suggestion would be to change the Ice Wind's pose a bit- standing perfectly straight like that looks unnatural, even for a robot. For the side poses it becomes hard to tell which direction the model is facing (I did the same thing with most of the 3D rendered character sprites, but that problem should be fixed soon) . If possible, could the feet be moved a little bit apart and the elbows bent?
The Roc is around 18m tall, the Ice Wind around 14m tall. For comparison the BuruBuru is 16m tall. Both sprites look pretty close to me, though I haven't lined them up. It's not important to get things exactly right so long as the impression of "bigger than the average mek" or "smaller than the average mek" is expressed.