Let's see......... GMK Goji is 60 meters tall and about 30,000 tons, whilst KiryuGoji is about 55 meters tall and 25,000 tons. GMK Goji is incredibly aggressive and tenacious, and is also a bit of a thinker as well, albeit only to a limited degree. KiryuGoji is a bit more passive, but is a real trooper in the field of combat. GMK Goji is an abomination of the souls of WWII and the origianl Godzilla merged to form the ultimate creature of vengeance, whilst KiryuGoji is simply a second Godzilla.
GMK Goji seems to be immortal, since even when blown up from the inside out by his own atomic breath, with only his heart remaining, he lived on, whilst KiryuGoji nearly died from the Absolute Zero Cannon exploding near him, saved only by the impact into the water, which caused some of the water around them to flash freeze first before getting to Godzilla, and even then left a very nasty scar that didn't permanently heal even a whole year after.
KiryuGoji was harmed by Human-made MASER cannons, albeit it not by an enormous factor, whereas GMK Goji managed to absorb the Gravity Beams of the guardian King Ghidorah. A large metallic blade of Kiryu managed to pierce the hide of KiryuGoji, whereas it took specialized drill-missiles and an already open wound to make a satisfying scar.
Overall........ I'd say GMK Goji trumps KiryuGoji by JUST a tiny bit more, but it'll be close, and KiryuGoji will learn a lesson or two from his predecessor revived from the grave.