Bitrate makes a massive difference to how smooth and detailed the video looks. Putting it as simply as possible the higher the bitrate the less video information is lost so the re-invented frames are much closer to the original data.
Anyone with a HD camcorder or DVD recorder will tell you that. At the same framerate the higher bitrate settings produces way better pictures than the lower ones at the expense of producing much larger files.
If you watch a blu ray with your fancy processing turned off it will look much superior to HD from broadcast TV even if you let the box de-interlace and double the frame rate to 50 fps. That's 24 fps compared to 50 fps.
You surely aren't saying broadcast HD looks better than blu ray ?
They both use the same compression codec, only difference is bitrate and frame rate.
You should try looking at the i frames of HD TV using a video editor zoomed into single frame resolution.
