'True HD' is at least 1080 vertical lines of pixels I believe and 'HD Ready' is at least 720. So both of those screens are technically HD Ready because they can display the required 720 lines. The first (20" one) displays 1680x1050, the latter (19" one) displays 1400x900. It's the second part of that resolution that you're interested in (1050 & 900) if you're thinking about it from a HD Ready/True HD perspective.
The second monitor is also more expensive because it has an integrated analogue TV tuner.
If you want something that can display 1080 (True HD) you'll need a monitor displaying running at a resolution of 1920x1080 or 1920x1200, which can be either 22/23" or 24/26" screens respectively.