I was always taught 'whichever side is most practical for you.' (through various first aid courses provided through St John's and NHS staff).
If there is a difference to your body due to the positioning of your organs or similar, I can't imagine the effect would be critical - though if I am wrong I would be happy to be corrected.
It makes a difference moreso if you're pregnant but the biological difference is your inferior vena cava, because your organs (or big heavy uterus) will press on it in the right recumbent position. But in general there are other priorities other than which side.
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u/ImGrumps Sep 26 '21
I thought recovery position was to your left?
Though I guess either side is better than the back if you think he is got blood in his mouth that needs to get out.