Faster? Why's that? NTFS is a more complex format (compared to FAT) - so the disk access will probably be slower. Don't think it will be significant, but in my opinion it certainly won't be faster.
Safer... well sure, FAT doesn't support access control, encryption and stuff like that - but if it's an external disk, it may not be what you really need.
OK, there may be one important point to convert to NTFS - on FAT partition you won't be able to create files bigger than 4GB, which is a limit these days.