Nearly a tie: Indonesia and Iran differ by barely -13%% in area — about 1,872,242 km² km² against 1,622,847 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 0.9× you see above.
The old map muddied it further: Mercator inflates Indonesia about 1× and Iran about 1.4×, so on a Mercator-style map this pair appears 1.2× apart instead of the true 0.9×.
Indonesia fits 0× into Iran.