Oceania is clearly the larger of the two: about 8,600,000 km² km² against 16,879,701 km² km², roughly 2× 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 6.1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Oceania fits 1× into Russia.