Given the increased page volume between the original module and the sequel you'd be forgiven for imagining that the sequel would have a larger area to encounter; but that's not the case.
Original Maps from pgs. 4 and 5
Sequel Maps from pgs. 4 and 5
Surprisingly there aren't a lot of differences between the two maps. In the sequel the lines are cleaner and more visually appealing. The water is easier to distinguish in the lesser cavern and the features of the map are far and away more discernible.
The big differnce between the two maps comes from the keying of each. In the original Lesser Cavern you have six non-combat encounter areas keyed (denoted by numbers) and 16 combat areas (denoted by letters). By comparison to the sequel you have 22 combat and non-combat areas all signified numerically. Most of the keyed locations occur in the same place on the map, but not always. For example, encounter 7 on the new map never occurs in the original.
In the Greater Caverns we see some more significant changes. Additional cavern features are clearly evident, such as the sink hole in location 7. The circular wall that encompasses the central area in the original map has also been removed. You also have the changes in encounter location that occurred in the lesser caverns and less keyed encounters in the sequel. In the original you have 23 keyed and signified by letters, while in the sequel you have 20 denoted numerically.
While you might be tempted to feel robbed by this shortening of encounters, let me put your mind to ease. The sequel more than makes up for this dearth as I'll be discussing later in this series