The YF-21 main body transforms in the same way as the VF-1, it folds in half and the legs, while not also doubling as the main engines, will transform more similarly to the VF-1 than the 19 ever will.
Also the 19 has no over the top backpack with powerful vernier jets, they are located underneath and pointing to the rear of the GERWALK mode. GERWALK also has the arms go over the top instead of underneath, the YF-21 is closer to the VF-1 in that respect. And the way that the main body of the YF-19 is COMPLETELY differnent, from the VF-1, only the nose folds down, and the main cockpit moves back instead of forward and down, again, the YF-21 is more similiar to the VF-1 in this respect. Forward canard wings are also present, making is look a lot different from the VF-1 but more similar to the VF-11 Thunderbolt. In terms of similarity, it is less similiar to the VF-1 than the VF-1 is, but yet at the same time it is completely its own entity, like the YF-21. I too, could cop out and say the YF-21 is similar, but the details are different, but I won't, cause it is unique in itself.