What I'm saying is beyond you because I'm not saying any such thing. You cannot compare 720p to 1080p and say there's not a "visible" difference on equipment that can show it and be sane.
What I am saying is that you don't need BD levels of compression (i.e. that low) to achieve the same relative visible quality the vast majority of the time. BD uses that level because that's the amount of space they have available and they're going to use as little compression as possible to fill that space. That's a reasonable thing to do, but it doesn't mean you couldn't get away visually with more compression. I'm saying a 1080p movie file at the 8-12GB range can be mostly/virtually indistinguishable from a 40-50GB BD movie with proper compression. That doesn't mean there are no differences (especially during certain motion events that move every pixel on the screen randomly that happens in some movies once in a blue moon) and it doesn't mean you could overlay them and have a pixel exact result. What it does mean is that the average viewer (yes with proper equipment at viewing distance where you can see the full resolution) isn't going to be able to pick out the BD from the compressed file with the movie in motion MOST of the time (i.e. when shown various repeated segments).
I realize most BD snobs wouldn't believe that for a minute and most would make strong claims that I must be blind, etc. if I cannot tell, but strange things happen when you do double blind tests on things like this. I've seen every claim imaginable in the high-end audio arena and let me tell you that 95% of them are pure unadulterated BS and this is with people that have ULTRA EXPENSIVE high-end gear. They have every psychological reason to imagine they are hearing better sound (who wants to admit they wasted all that money?), but usually no technical/scientific reasons. The double-blind test is THE only way to prove perceptible differences with humans.
Most people making blanket statements do not take into account other factors involved either. For example, you may say an Apple TV downloaded 720p movie looks like "crap" to you on your 1080p set. I've seen that claim before on here. The problem is that a 1080p cannot show a 720p signal without scaling it upward. There are a lot of crappy scalers out there (just like with progressive DVD players there were a lot of very AWFUL scan doublers out there). You cannot assume what you're seeing on a non-native display is an accurate representation of that signal without a frame of reference. I have a 720p projector with a 93" screen and a 46" 720p plasma tv. They show true 720p and so I don't get distorted signals from 720p sources. Given the vast majority of sources are 720p or 1080i (neither of which carry 1080p resolution and both of which must be either scaled or line-doubled in order to present it on a 1080p resolution display), I'm not convinced a 1080p set is automatically a "good" thing (unless all you ever watch is Blu-Ray).
A good example are my two 24" LG monitors I have in my den on two different computers. They are both the same native resolution (1920x1200). One cost $600 at the time and the other cost $300. At 1920x1200 they look identical to my eyes. The difference, however, becomes clear when showing lower resolutions. The $300 display looks like CRAP at non-native resolutions (blurry/smudgy/unclear looking) whereas the $600 display looks only slightly off native clarity at lower resolutions. The scaler quality is night and day between the two. If you're going to use native resolution all the time, the cheap one is just fine (I use it with my Macbook Pro and it looks great). But the $600 monitor I use with my gaming PC rig and I can turn down the resolution on newer games that my GPU cannot keep up with at maximum resolution and it still looks great. The same games on the other monitor would look well...less than optimal.
The same thing happens with 1080p televisions showing 720p, 480p,480i and even 1080i sources. Things get a little more complicated with 3:2 pulldown and other issues, but ultimately you cannot "assume" just because 1080p looks "great" on your set that a 720p source looks like total "crap" just because it happens to look poor on your particular set. Yet I see that assumption and argument all the time. 720p sets are far less common today and so most people have never seen 720p sources in their native resolution and thus go by the image they are getting with their particular scaler, which may be good or it may be bad or somewhere in the middle.
Then there's the matter of optical resolution perception limits. For example, if you view a 1080p signal on a 42" 1080p monitor, you are not seeing 1080p worth of resolution at 10 feet away. You are seeing something closer to 720p worth of resolution and thus there is no real benefit of a 1080p monitor if that's where your seating location is. If you sit 20 feet away, you might as well just watch a DVD because you won't see more than 480p worth of resolution. I mention this because I've seen plenty of comments of people about 1080p superiority over 720p and the people in question weren't even seeing 720p worth where they actually watch the set (telling a difference at 3 feet for demo purposes is meaningless to your actual day-to-day experience).
Thus, I am in no way saying that 1080p isn't potentially beneficial assuming you have the right sized screen at the proper distance that you can actually see resolve that resolution and I'm not saying that under no circumstances can a Blu-Ray show a difference compared to using 5x more compression. I'm saying MOST of the time those differences are negligible to the point where it would not be worth using 5x the storage to have BD levels of compression on a hard drive storage system. It's certainly not worth it to me to have to keep using a disc based playback medium. I'd rather transfer the movie into a format that is useful for broadcasting around the house and doesn't take up an entire 3TB drive for a mere 60 movies when I could easily fit 300 movies in the same space with almost no drop in quality and more like 500 at 720p resolution for my current projector system with no noticeable drop in displayable resolution there (and perhaps a quality bump where the scaler performs worse in real time (that a BD player or projector would have to do to show 1080p on a 720p projector) than a high quality transfer to 720p).
