Argentina is clearly the larger of the two: about 2,782,703 km² km² against 1,872,242 km² km², roughly 1.5× at true size. Drag one onto the other on the map above to feel the gap.
Argentina sits in South America, Indonesia in Asia. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1.5×.
The old map muddied it further: Mercator inflates Argentina about 1.5× and Indonesia about 1×, so on a Mercator-style map this pair appears 2.2× apart instead of the true 1.5×.
Indonesia fits 1× into Argentina.