Closer than most people guess: Iran (1,622,847 km² km²) is only about 19%% larger than Saudi Arabia (1,925,871 km² km²).
Both sit in Asia, so this is a same-region comparison: the new Equal Earth map draws both with the same honest geometry, and the real gap is exactly the 1.2× you see above.
The old Mercator map treated both about equally (1.4× vs 1.2× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Iran fits 1× into Saudi Arabia.