There is a little known reason why games typically look and perform superior on the 360:
http://www.escapistmagazine.com/news/view/112562-Microsoft-Doesnt-Want-Sonys-Sloppy-Seconds
That's not the only reason though. The 360 have a better development tools and hardware that is more suited for games, thanks to their multiple general cores, a slightly more powerful GPU which is blessed with some embedded RAM and a unified RAM that is shared by both the CPU and GPU.
The advantage of the PS3 hardware are the SPUs, which are
blazing fast at what they do. But unfortunately there isn't really much game related stuff they can do, so in the end it's not much of an advantage. What the SPU is really good at, is to decode and play video streams, it could probably play hundreds of high quality videos at the same time, but that's pointless to do in a game.
Anyway, clever people have been able to use the SPUs for other things than just videos, fortunately, there are physics calculations, collision detection and postprocessing effects like MLAA (as seen in God of War III or Soul Calibur V to mention a few) and motion blur (as seen by moving the camera fast in the Uncharted games) that the SPU can do most of the calculations for, but that's kinda it.
Physics is the big SPU thing as far as Skyrim is concerned I'm sure, as there is no doubt Bethesda used the PS3 SPUs for physics calculations, thanks to Havok. But I'm not really sure how much else Bethesda would be able to move over, without spending a year or two trying to port as much of their general code to SPU code as possible. Just me guessing though, obviously.
But to port a game that is designed for two general cores to one general core and SPUs is not a walk in the park. We have plenty of evidence for this, as a great number of games have failed with it; Baynetta, Red Dead Redemption and many others, where the 360 version is clearly superior. In the past the Namco fighting games been vastly better on the 360 as well, it's first with the recent Soul Calibur V they managed to make both versions even.
Oh, and the blu-ray drive is completely irrelevant here, seeing how Skyrim is less than 6GB anyway. Even the 360 disc is far from being filled.
Don't think I'm biased towards the 360 either, I don't have one, but I do have a PS3 and I
am pleased with it. I'm currently playing Way of the Samurai 3 on the PS3 (when I'm not playing Skyrim on the PC), which is quite buggy and quirky, but still a lot of fun!