Just sticking my oar in re. the AR discussion - Citizen's ARCT has a checkbox that you can use to decide whether or not you want to comply with the ITU standards. 1920 x 1080 HD video with square (1:1) pixels downsizes to 16:9 PAL as 702x576 if you follow standards, or 720x576 if you don't.

I really don't think it matters too much either way - aspect ratio errors on old CRT displays could easily be much higher than the 2.5%, and I suspect many modern displays don't scale things perfectly either. Is a 2.5% error noticeable? How much "error" do you get when your display isn't orientated at exactly 90° to your viewing position?

It'd be interesting to check the dimensions of the test cards on DVE, or the THX optimizer, to see whether the circles displayed follow standards or not...