These are different token formats.
- UUID is the default format that can be used for any kind of data. With UUID, tokens will look like
tok_live_fgiC3Jx2abPUOPETFMvXuT.This format helps to quickly distinguish tokens from regular data additionally makes it easy to distinguish production tokens from the sandbox tokens.
- FPE 6_T_4 is the format-preserving format for card numbers. With it, the token will look like card number and will be a valid card number with the same first 6 and the last 4 digits. It is useful when tokens need to be valid card numbers e.g. to pass validation but if you don't have such requirements, the default UUID token format is the better option. .