Don as the TP2 page you linked says: "This is basically just TP1 + all the updates."
The reasons you might want to re-flash is that it has new partitions layout allowing tri(quad*) boot:
Bootloader, which is handy if you want to try out new kernels that might fail and still get back to a working system with a different key combination, or if you want to try out sailfish etc.
* - quad if you include recovery.