Too many factors:
Here’s a good article to help (not much) decipher the difference in need.
Conclusion for link above:
The effective work requires few of RAM.
Fast work with small and average directories.
The disc implements less movements of the heads (as compared with NTFS).
The effective work on slow discs.
Quick performance decrease with the fragmentation going up (only for FAT32).
Difficulty in access to big files (more than 10% of the disc space).
Very slow work with directories containing huge amount of files.
Fragmentation does not influence the system performance (the work might became worse as far as data access is concerned).
Complicity of the structure of directories and the number of files do not affect the performance.
Quick access to the required file fragment (i.e. editing of big .wav files).
Very quick access to small files (several hundreds bytes) – the whole file is located in the same place as the system data (MFT recording).
The memory size mustn’t be less than 64 MBytes.
Slow discs and controllers without Bus Mastering slows the system performance down tremendously.
The work with average-size directories is quite difficult, since they are fragmented.
The disc working for a long time with 80% – 90% of its space occupied shows low performance.
Remember, that the RAM size is the chief factor influencing the system performance. In case of 64-96 MBytes both NTFS and FAT are equal. If you are using only an OS and simplest applications, FAT32 might turn to be better on the PCs with bigger size of memory.
NTFS is still a system for future. On the typical game system it won’t show the brilliant operating speed. The main advantage is that the complicity of directory structure, disc size, fragmentation do not have an influence on the system performance. In FAT, on the contrary, all these factors slow the operating speed down.
FAT 32 is the better choice for simple users’ systems. As for graphics workstations, office computers with thousands of documents and moreover file-servers, NTFS shows higher performance.