The major differences between the two are that one supports up to 720p and the other up to 1080p, and of course $200 (which aren't really a concern to me).
I am planning on playing games on the TV and watching movies, and I'm very picky on the performance of my games (I require them to run at 60fps average, 30fps is just not fluid for me). I am familiar as to how the image distorts on computer LCD screens when ran on a resolution other than it's native (and quality drops considerably), and I'm assuming LCD HDTVs suffer from the same problem.
For the time being I am able to afford a HD 4850 graphics card. So the main attractive for me to get the LN40A450 is the fact that it runs 720p resolution natively, so the image will not be distorted, even though it would be of lesser quality than 1080p.
My question is the following, if I were to get the LN40A550 (native 1080p model) and run it in 720p, would the image quality be degraded beyond that of the LN40A450? (native 720p)
I would very much like to get the 1080p model, but it's just a no-go if I'm unable to run it on 720p with an acceptable level of quality. (I understand it won't match a native 720p)
I would have to say go with the A550 if price isnt really an issue. and if you are wanting the faster frame rate you might want to look at the LN-40A650 with the 120hz insted of the 60hz that both the A550 and the A450 both have and it has a 4 millisecond response time. So it will have the fastest frame rate and with the better graphic card you will be able to reach the better pic qalitiy with the a650 cause it has a 50,000:1 contrast ratio, the A550 is 30,000:1 and the A450 is 20,000:1 But back to the question if you go witht he A550 you wont have a problem with the pic being distorted. and your pic will not be downgrated if you do go with the A450 you still will get a great pic and all the tv will do if you sent a 1080p picture to it all you will see is the 720p picture