HD series will privide a native resolution of at least 768 (Physical number of pixel rows) vertically which would enable them to reproduce a HD 720p signal without down-interpolating lines (it seems that the eye is more sensible to vertical rezolution rather than horizontal). With Pannies you would get HD displays in 1024x768 for 37' and 42' diags. and 1366x768 for 50 and 63.
Then it's also a question of total number of distinct colours a display can generate. Older generation HD panels (including my TH-50PHW6) were able to display around 1 billion colours, some other went up to 4 billion. Newer generation panels, especially non-HD go up to between 8 and 16 billion (the TH-37PV500 will display more than 8 billion). Some people can rate this as a better image and they have reason to do so. The difference between a 1 bln col display and a 8 bln col. diplay should be noticeable especially in areas with darker colours, where plasma display exhibit a rather benign form of local flicker.

Im my rather limited experience compared with other fellow forum members, I can say that some Pioneer HD models (they understandably prefer 1280x720) seemed to me to offer perhaps the best overall image quality in their price bracket, having at the same time high resolution, high number of displayable colours and well implemented internal mapping/filtering algorithms.

Ultimately, one ca think of applications first:

Will there be a lot of time spent using the plasma as a PC display (for gaming, browsing, etc) ? Here the HD will have an advantage (just try to read those small fonts on a 852x480 native rez display when attacking it with a 1024x768 -in squeeze mode- 1280x800, 1280x720, or 1366x768 display card output ...). Same would go for a hi-rez gaming box.

Will there be a lot of time spent watching original DVD's in PAL format, or HD sources in 720p or greater ?

Coz' if you mostly watch analog CATV, air TV or NTSC DVD's (480) it's not going to matter a lot ...

Does one value more resolution, or the color richess (sometimes you find them somewhat exclusive in quite a few plasma displays) ?

And do you look at your 1000-2000 quid as a long-term investment?

well ... maybe I did split the hair a bit too much smile

M kit : G08 502 557 507 2xDSP5k