1080p coming from a streaming source is not going to look as good as 1080p from a bluray.
however i streamed the same movies on 360 and ps3, on their own amazon prime apps, and the quality was SIGNIFICANTLY better on the ps3 version. again, not netflix, but it doesn't surprise me that netflix on 360 is worse quality than ps3.
why? i have no clue.
I thought this true until I realized it's (at least for me) because the Xbox's wireless blows. Sitting right next to each other the Xbox was struggling to keep up while the PS3 was fine. Plugged both in wired and the pictures looked identical to one another.