Polywarmtone has a warmer tone than MGWT and has a different and i believe a more straight curve than MGWT which has a fairy steep curve with a more pronouced shoulder. Polywarmtone is also easier to manipulate with different toners.
MGWT is a great paper and i use it now that my Polywarmtone stach is gone but should we get Polywarmtone back and with the same characteristics i will switch back momentarily.