To those that would reply: keep in mind this is only in reference to displaying of text on a LCD HDTV, not a computer monitor. Computer monitors typically will have higher native resolutions the larger the screen size. I also have no intention of comparing fonts and/or font rendering betwen XP and X when using a computer monitor. This is only for those of us who are wanting to connect to an LCD HDTV, which for the most part are 720p (typically 1366 x 768 rather than 1280 x 720), while even my 15" MBP screen is 900p and most computer monitors of 24" and above are at a minimum 1200p and above.
Total of about 4 hours now into googling, reading, and adjusting settings; about all I can say is OS X is way behind MS in regards to font rendering on an LCD TV. My PC (XP) displays text on my sony 26" (720p) as clear as my MBP does on it's 15" (900p) screen.
MS's ClearType uses sub-pixel rendering.
OS X uses anti-aliasing and font smoothing (their implementation of sub-pixel rendering)
A fuller view and explanation is available
here.
They give a better score to X than XP on the technical side of font rendering, and that may be the case with a monitor. But, I can tell you they never connected each one to an LCD HDTV and tried reading.
Did not find anything in my initial searching about what settings to use in order to obtain the best looking text. So, trial and error, and an hour later I determined that the best setting was to altogether turn off font smoothing. After I figured this out, did more googling, with new terms, and found 3 other forum discussions where the members had come to the same conclusion. I personally could see no difference between the light, medium and strong options of font smoothing on my HDTV, that made one any more readable than the other.
To turn off font smoothing - System Preferences, Appearance - change Font smoothing style to "Standard - best for CRT". This leaves anti-aliasing turned on, but turns off the sub-pixel rendering best I can determine. Once you set this, the option below for "text smoothing font sizes" basically does nothing since it is now turned off. Also found a way in terminal to turn it off based on picking a font size, say of 100, but this is easier. Even with this setting, text is not very good at all. Remember to change this back to Automatic (or whatever setting you use on your MBP) after disconnecting from the HDTV.
I would suggest trying the different options to see what looks best to you. Especially since none of them look very good at all. For me this is yet another consideration for OS when I get ready to build a new system later this year. Will have to realize with a MacPro I definitely will have to move to a real monitor in lieu of being able to use my HDTV.
Note: While experimenting with font smoothing options, realize that these changes do not take effect until you restart the application. I used the Apple and mac-forums home pages for my tests. Kept Opera open to pages I was reading while making the adjustments and set Apple as home page in firefox and quit and re-started it after each change. Found comparing the blue text (links) on the Apple page gave me a better indication of the changes than looking at the black text. The black changes, just more subtly.
If you are not using "Standard - best for CRT" - under changes to the text smoothing for font sizes - if your text looks jagged, decrease the point size - if your text looks blurry, increase the point size.