Bit rate has a far more obvious and even jarringly noticeably difference than resolution. The reason Blu-ray easily blows away what can be seen on cable, sat, etc., or local HDTV directly into the TV is because of BIT RATE!!!!!! Presuming a an OTA digital HDTV source at full resolution, ATSC can only provide about a maximum effective 19Mbs for all video, but keep in mind that most broadcasters have sub-channels on that same bandwidth, so the main HD channels is actually LESS than the best case 19Mbps, perhaps only at about 10Mbs (or even less in some extreme cases). That is about ONE THIRD the bit rate of some of the best Blu-ray discs out there that average about 30Mbps and can even peak around 40Mbps. This is also why many consumer HD cameras never provide an image as good as Blu-ray because most consumer cameras, while providing full resolution at 1920X1080, are limited to about 10Mbs. The best any channels sends to MVPD's is at 19Mbps, as those channels have adopted the ATSC effective 19Mbps as their own limit (they can send higher bit rate if they wanted to, but it would cost in bandwidth for their place on the satellite they use to sent to MVPD's), but the can and do in a number of cases send LESS than 19 Mbps. So, essentially, 19Mbps is the top end "standard" and best bit rate for any TV source and about 30Mbps for the best Blu-rays. That's the difference we can all see like night and day, less so than resolution as long as the reduced resolution isn't too low. Also, this is why a lot of people have a very had time telling 720P and 1080i apart because it is the BIT RATE that has the far more noticeable effect.
Here is a response I posted in another thread with virtually the same question/concern:
I think he is referring to the fact that for 1080i channels, Dish re-encodes it at the 1440X1080 HD approved standard and not the 1920X1080 resolution that is sent to MVPD's by the channel content providers. Some folks grumble about this slightly lower resolution, but it is among the approved HD standards (some OTA broadcasters are doing this, too). However, it is often bit rate, not necessarily slightly lower resolution, that can have a much bigger impact on HD PQ (DirecTV's Ka sats used for its HD channels have transponders with greater bandwidth than Dish's DBS Ku sats it uses for HD channels, so DirecTV has an advantage there). In other words a full 1920X1080 at a lower bit rate can look WORSE than a 1440X1080 higher bit rate. In addition, the Dish STB's can further take advantage of low bit rates and resolutions with software and processing before outputting to your HDTV that can provide a PQ that looks like it was sent at higher bit rate and resolution. Also, there are other ways of reducing the data needed on a xpndr or OTA channel that could also be worse to PQ than slightly lower resolution such as lower chrominance data, lower luminance data, etc., but the use of Turbo Coding (used by Dish for HD channels) can allow for higher throughput (more data) in the same limited bandwidth, thereby not having to reduce other picture data nor use as much compression than without Turbo Coding.
Also, one has only to view some of our LA OTA digitals to see how inferior the HD PQ is when local broadcsters are running an HD channel at about half the bit rate OR LESS, even at a presumed full resolution rate, but to accommodate other multiplex (sometimes referred to as sub-channels) channels on the same stream, and KABC shoving TWO HD channels (at 720P with the 2nd HD channel at a noticeably inferior PQ that is probably at a lower bit rate, and it could also be at a lower horizontal resolution) and an SD takes it toll, especially since OTA broadcasters are stuck using MPEG2 (instead of the far more efficient MPEG4--more channels using less bandwidth with superior PQ--as Dish and Direct do) and an effective maximum 19Mbs bandwidth in which to cram all this. I have found Dish's 1440X1080 to be often superior to some of our big network locals I have viewed LIVE using OTA antenna via TiVo or DIRECTLY into my HDTV. Yes, FiOS would be noticeably superior at the full 1920X1080 at a generous bit rate, and I would love that in the perfect world (FiOS can't necessarily improve the inferior OTA being sent to it) but I've found that Dish HD running directly into my TV can be pretty impressive, and even more so with my AV receiver processing chip and a DVDO on another HDTV. I find it an acceptable compromise. However, I understand why some do not, and are irked by it, and I agree it ought to be full resolution for those fancy HDTV's we buy, but except for FiOS, nobody achieves that, not even most broadcasters. I will say that KCBS seems to be noticeable superior to ANY other LA OTA and I wouldn't be surprised if they are running full resolution at full bit rate. Keep in mind that while Blu-ray can provide around 30Mbs, I don't think there is any HDTV channel content provider running at more than 19Mbps per content "channel" to MVPD's. Once you start watching Blu-ray enough, even the best full resolution at full bit rate OTA starts to look pretty diminished and not so impressive, after all.
