Same thing with BF3, Xbox users have the option to install it, the install makes textures better
Not the same thing with BF3.
BF3 has an optional install for the normal textures and without it, it loads low res textures from the DVD.
That's not the case with Skyrim. There is no optional texture install or anything like that. Just the normal install feature of the Xbox360 itself.
Installing games on the HDD doesn't change quality of the textures. Just helps with texture streaming and loading times.
But apparently there is a bug, which causes streaming errors if you install Skyrim to the HDD on the 360 so it looks worse than playing from the DVD.
Probably fixed with the day 1 patch.