Yes there is difference and its called compression that the dev did not do. A compress version is the full version of the game.
And your point of view of not trying a "Compress" version really does not make any since.
I mean, if you're using lossless compression, sure.
Otherwise, it's a valid sentiment to only want the original.
Bandwidth and hard drive storage is cheap for most, what's a few hundred megs these days.
Now if it was 150GB vs 50GB, then maybe; but even then...
Or if you're on dial-up, I guess. Remote locations don't get fiber.
Edit: I've tried the compressed version for a spin, and the compression artifacts are noticeable, no effort to notice, really, right upfront.
The main menu screen mirror reflection, original scene - you have render noise, compressed - jpeg artifacts.
Other places - detail lost, artifacts introduced, in places like hair, wall textures, etc.
Fine if on a really small screen; or if 900M is a lot for you, I guess. Or if you just don't care. But otherwise...
