The PassMe2 is a new revision of the code on the CPLD of any regular PassMe, that allows the passme to be used on DSes with newer Firmware. However, the PassMe2 is not as flexible as the original: it is tied to a particular DS game and requires a Flash cartridge with SRAM to use.
Because the PassMe 2 requires that you have a Flash cartridge with particular SRAM contents in it during every use, we recommend that you use the PassMe 2 to install FlashMe, which allows you the flexibility of using other cartridges like the GBA MP or development via WMB.