This is just my opinion, but...
When I was researching an HD TV, I did a LOT of research. Ultimately, came to the conclusion that most of the upper-level brands (whatever consumer reports would give a nod to) are pretty damn good, and the differences in picture at that point are going to be discernible only to the true videophile.
In otherwords, I think the 'quality curve' on the graph tends to level off once you hit the tier of decent name-brand sets.
There are DEFINITELY differences and some will really be interested/annoyed in those, but I, in the end, realized I was not one of those folks and that going nuts with research was going to end up being a waste of my time.
Personally, I'd rank the decision on:
- is it the right size?
- is the picture 'good enough' for your eyes?
- is the remote/on-screen menus a decent interface?
- does it have enough ports in the back?
Every store touts the contrast ration numbers and brightness, and all that, but, honestly, those numbers don't mean much without context...namely what your personal opinion/tastes are and the room your TV will be sitting in.