Dave said:
First off the best picture you can get right now is OTA Over The Air with a antenna.
This will give you the best HD picture available.
Second, all signals over cable, Satellite, or Fios is down rezzed. Actually it is down rezzed twice before you ever see it on your screen.
The actual channel that is shooting the show down rezzes it the first time so they can send it to the cable, satelitte com, or who ever to send it to you. Then the Sat company, cable company or who ever down rezzes it again to fit into there bandwith parameters. This is a fact of life. The cable, sat , etc. companies only have so much room on there systems for so much content. No company right now can give you full HD content in full HD. Fact of life. You, I or no one on here can change this right now. Yes some companies do us less down rezzing. But they still only have so much room on there system for each channel.
Don't confuse "downres" with compression. Downres implies less resoultion, and that is not the case on nearly all channels on DirecTV or most cable systems, most of them send exactly the resolution they are getting either 1920x1080 or 1280x720. (Dish is a ? mark for me here, I think I read they had all HD at either 1440x1080 or 1280x720).
OTA is going to be a crapshoot no matter where you are, multicasting can absolutely kill a great HD source and make it look like upconverted SD. So don't fall into the trap of thinking the broadcasters have an advantage. They get it from the networks just like DirecTV, Dish or cable companies do, and by the time they finish draining off the bandwidth for subchannels its usually just ok as far as quality is concerned.
All HD you will EVER get in your home will be compressed, nobody can afford the backbone it would require to deliver uncompressed HD to the end customer, it is on the order of 1Gb per second for one stream.
Something else to note is that a lot of "broadcast" cameras can only capture at 1440x1080, so it is questionable whether or not you are even seeing "true" 1920x1080 from ANY source other than film transfers.
The thing to do is look at the channels YOU would watch and decide if it is acceptable to you.