I prefer Style 1. You can view both skyboxes at the same time and compare them.
Style 3 is cool, but the constant change (flickering) of the image prevents me from looking closely at small details. The flickering of bright colors on the towers quickly tires the eyes. And when I imagine a Download page with a bunch of these flickering images ... ugh…
Style 2 would be the best, but only if you could manually move the slider left and right. So, that leaves Style 1.
Anyways, awesome skyboxes!