North America is clearly the larger of the two: about 24,710,000 km² km² against 8,600,000 km² km², roughly 2.9× at true size. Drag one onto the other on the map above to feel the gap.
The old Mercator map treated both about equally (1× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Oceania fits 2× into North America.