When you start using Sky and Freeview services to compare PQ, you have to remember a few things. The MPEG coding on channels can be statistical multiplexed, so at any one time depending on what other services and content are being carried picture quality can go up and down by the second. You should have both panels lit simultaneously on the same source and split field vision to determine if one is really doing better than the other. If one manufacturer uses better tricks then poor MPEG might seem better on some pics compared to others
It's interesting to read that many may have comitted themselves to an HD panel, before services are available and may now be making their comparisons of new panels on existing low bit rate Sky services. If you just want Sky SD on a plasma, look no further than a cheaper lower res panel, as it's likely to look better. If you really want to compare 2 HD panels from different manufacturers then look for the review that does this first on the same HD source test material, streamed as digital video off disc and not a stat muxed transmission. When that's done, the receivers and MPEG decoder will play their part and this is where some tricks may be offered in setup menus to ameliorate artefacts - but usually they bring unwanted secondary effects.
I wouldn't be happy if the shoot out favoured manufacturer 'A' on tests using low bit rate SD services, then when HD services started, manufacturer 'B' won in a direct comparison because everybody was now saying the pictures were sharper!