The two systems are a little different in design in that +FAT is designed for multi-threading systems and protects data structures [with mutexes] at a lower level, just where it needs to, whereas FatFS makes itself thread safe by using mutexes arround entire API functions.
As for status; whereas +TCP is just about ready to be in the main FreeRTOS repository (although it is not undergoing some new feature development), the +FAT code still requires some ‘FreeRTOS-ification’ in that the code does not follow the FreeRTOS style in all places yet.