If you're desperate to play the game now then get the 360 version now and trade it in for the PC version later. The 360 version will run you £39.99 +/- £5, the PC version can be had around £25 now, the trade-in values for the xbox version should still be fairly high by xmas.
If you want to know what the PC version of the game can offer you that the xbox version can't just head on down to TESnexus and browse the mods.
Content alone: New weapons, armour, items, playable races, entire new areas to explore, new quests for Cyrodil and the new areas, new enemies.
Aside from adding content mods can significantly change the way the game works, the levelling system can be completely revamped, the magic system, the damage system, the combat system, everything.
Oblivion also had a massive range of texture, lighting and other graphical enhancement mods that made it look less like a came that came out over 5 years ago, although these probably aren't necessary now, in 5 years time Skyrim on xbox will look like a 5 year old game while Skyrim on PC won't. Modders also made a lot of changes to facial and body textures so the women look more like women and the men look more like men instead of everyone looking like midding unisex weirdos with half of them having weird chest bumps approximating breats.
Also worth noting is that the "Unofficial Patches" for Morrowind and Oblivion contain thousands of fixes Bethesda never bothered to fix themselves.
And it's all free of charge.