From my knowledge, Paper 1 and Paper 1R are the same level of difficultly and cover the same content (the R stands for Regional).
The reason for the different papers is due to time zones. Students, for example, in the Indian subcontinent will sit one paper, whereas students in Britain will sit the other. This is to prevent cheating and swapping answers between the two areas - as one country will take their exam before the other.
Hope this helps!