I am not here to bash DirecTv and have people switch to another provider. I do not care about that. I am a DirecTv subscriber right now with a year contract and bought all the equipment so I have a whole lot invested own it. I am also a Dish Network subscriber and I have bought my equipment as well. So I have nothing to gain by conveying my observations. I have trash to the ground Dish Network as well for their sometimes questionable moves. So I am here as a simple subscriber trying to tell you what I see with my own eyes about the HD channels.
OTA Networks This one is very hard to generalize. Every OTA channel when compare with HD Network, carried through DirecTv, is different. In my area (NYC), the OTA is quite acceptable and I am for the most part very happy with the job that the stations do. When I compared the OTA channels in my area to the DirecTv HD Networks like CBS HD, ABC HD, NBC HD, & Fox HD, the OTA wins. There's no argument about it. I rather see these channels through my Antenna (OTA) than DirecTv. Reasons: these channels through DirecTv are very soft and show compression artifacts. My experience may not translate to your area for OTA Networks. In fact, it is possible that for your area, the OTA Networks may be providing less bandwith and compressing more than DirecTv. This is why it may not look any different to you. I also get CBS HD through Dish Network and I can tell you that CBS HD through Dish Network and my OTA CBS HD are identical.
HDnet, HDnet Movies, ESPN HD & Discovery HD
I have compared Dish Network and DirecTv on these channels and Dish Network Channels are far superior in Picture Quality (PQ). These channels on DirecTv are very soft and lack vibrant colors. Also, the 3D effect or WOW factor are gone on DirecTv. You can still see the 3D effect or Wow factor on Dish Network.
Universal HD This channel is at best 480p. But I think my DVD does a better job. Any simple movement and you will see motion artifact like you have never seen before. On still pictures the PQ is so soft and watch out. Very hard channel to watch.
Showtime HD I have made no comparisons on DirecTv but movies that are 2004 and you know that the transfer is supposed to be much better than what DirecTv presents are not being shown. I looked at the DVD for comparison and showtime is a 1080i upconvert. I am not talking about the upconverts in Showtime. I am talking about what is supposed to be HD. The channel has this watch out and soft look.
HBO HD I have nothing to compare right now. But it looks decent but from what I remember from VOOM and Dish Network (when I had it), something is funny but I can't comment on it.
Channel 94 YES HD This channel looks fabulous on DirecTv.
Channel 95 FSN WEST HD I saw this channel when DirecTv had the MLB free preview and HD baseball games from FSN WEST looked awful. I thought that it was a production problem but I asked a few Dish Network customer who are also getting these games in HD and they do not seem to see the same problems.
This is just my assesment. It may not count by much because I do not have bitrates data. But it is my observation of what I am seeing. Vurbano posted the link to the bitrates already. To me it does not matter how much $$ I invested in any provider, if the HD channels are bad and I cannot watch them, how could I go blind on that. I wonder why DirecTv couldn't do a better job with these channels. Voom had less bandwith and some of their channels at 1440x1080i looked very good and they did not degrade the HD channels so much. This is no exaggeration. If you ONLY have DirecTv, you may not be able to compare, but try to make comparison with another provider and you will see the difference.