FAT32 uses smaller cluster sizes. There's an upshot and a downside to this: The upshot is that it makes more efficient use of disk space, the downside is that the filesystem tables are larger and consume a bit more memory. I'm not sure whether in reality FAT32 is faster than FAT, but it is supposed to be.
I don't know how well the conversion tool works, sorry. Regardless though, I would advise backing up the data first.
Reliability, in my experience is no different. The stability of the OS is the problem there, not really the filesystem, practically speaking.
