I'd like to ask for a comparison in quality of streaming 1080p movies via Netflix or now Apple iTunes compared to the traditional blu ray disc.
What's the best Stack Exchange site to do so?
If this isn't a subjective question, I think that movies.SE would be suitable enough for this purpose.
Ask yourself: Can this be answered 20 ways or just 2? If you answer yourself "20 ways", there's no Stack Exchange site suitable for your question.