[MC] An advantage of clustering for a file allocation table is the file allocation table is smaller.

There are fewer clusters than blocks. Since a file allocation table holds one entry for each cluster, the table is smaller.

Clustering has advantages for other file systems. Fewer inodes are needed for large files. Clustering also helps to keep a file at least partially in contiguous blocks, which speeds up reading or writing the file.

The main disadvantage is internal fragmentation. Typically, the last cluster of a file is only partially used, with extra wasted space. A small file takes one cluster instead of one block on the disk.