The two maps are identical. They represent the same world and both show all the islands mentioned in the series.

However, there are 2 differences:

The small version shows the names of the great seas: North, South, East, and West Blue. Also, the Grand Line and the Red Line.

But the large version also has the names of the kingdoms, islands, cities, and other locations in the world written on it.

The small version measures 78 cm x 52 cm.
The large version is much bigger, measuring 153 cm x 102 cm.