50" x10 plasma has higher horizontal resolution with 1366x768

Yes you are right. In both cases, the image received will have be to scaled. True 720p (16:9) is defined as 1280 X 720. The displays we have are either 1024 X 768 or 1366 X 768 for non Full HD. Each case requires the horizontal and vertical pixels to be scaled either upwards or downwards. If you do not like scaling you need to get a 1920 X 1080 display and feed it 1920 X 1080 source (ie, Full HD, Blu Ray or others).  The eye is more susceptible to vertical resolution then horizontal resolution, that's why the 1024 X 768 displays rarely look bad.

Since some form of scaling is necessary, the most important aspect of a non 1080p source would be the quality of the scalar chip that resides in your HDTV. Some use better scalars than others. Bottom line, 720p will always be scaled, of course 480i (NTSC) and 576i (PAL)  will have to be deinterlaced (since all HDTVs are progressive, except one) and then upscaled to fill out all the pixels in you HDTV (be it 1024 X 768 or 1366 X 786 or 1920 X1080). This is what makes the difference between the sets.

Yes you are right. In both cases, the image received will have be to scaled. True 720p (16:9) is defined as 1280 X 720. The displays we have are either 1024 X 768 or 1366 X 768 for non Full HD. Each case requires the horizontal and vertical pixels to be scaled either upwards or downwards. If you do not like scaling you need to get a 1920 X 1080 display and feed it 1920 X 1080 source (ie, Full HD, Blu Ray or others).  The eye is more susceptible to vertical resolution then horizontal resolution, that's why the 1024 X 768 displays rarely look bad.

Since some form of scaling is necessary, the most important aspect of a non 1080p source would be the quality of the scalar chip that resides in your HDTV. Some use better scalars than others. Bottom line, 720p will always be scaled, of course 480i (NTSC) and 576i (PAL)  will have to be deinterlaced (since all HDTVs are progressive, except one) and then upscaled to fill out all the pixels in you HDTV (be it 1024 X 768 or 1366 X 786 or 1920 X1080). This is what makes the difference between the sets.