re: I recently "downgraded"
XGA 1024x768 was a standard IBM computer display, particularly with built in hardware processing to offload video processing from the CPU. Using that hardware processing, could be a cheap option for plasma displays, that appear to have been mainly made for the US market.
Plasma displays may not to be made with square pixels. So most non-square pixel plasma displays need to use additional processing as well as the 4:3 'scaler' that has been built into all digital receivers.
Divide 1024x768 by 256 and you get 4x3, obviously not a 16:9 display if the pixels are square.
The "apparently square pixels" cannot be square they must be rectangular - wider than their height in the ratio 4:3, to produce an actual 16:9 display
For a non-square pixel display, a full 1920x1080 video being received would generally be transformed from 1920 by 4:3 into 1440 in each line, to change square pixels to display on the rectangular pixel display.
Except that the UK transmissions on DVB-T/S are now generally compressed by the 4:3 scaler to reduce 1920x1080 to 1440x1080 etc - so such a compressed picture displays without processing if the pixels are displayed 4:3 shape rather than square.
So generally the 1024x768 plasma display does not have to rescale the pixel dimensions, for UK HDTV.
That leaves the built in processing to resize the picture, from 1440x1080 to 1024x768 - which is the same reduction in each dimension: (1024/1440)*1080=768 Rather than being done by a CPU this could be done by the cheap old hardware that was made for the IBM XGA displays.
Compared to very early plasma displays that sometimes had to process broadcasts with three picture transforms, this 1024x768 plasma display is generally performing one resizing transformation, in order to reduce definition by about 30%, which should be noticeable. Depends what you are watching, at what distance, and all the other qualifications. You would probably notice a difference between your old 1920x1080 LCD-TV and the new 1024x768 plasma-TV if watching a Blu-ray 1080p video.
However the better colour of new plasma display, compared to an old LCD display, is probably more satisfying for the moment, until the plasma display deteriorates with age.