Imo, the main advantage of the Hi Metal VF1 is the superior hip articulation ; the ball joints are in these sliding capsule joints, which make it possible to get a true wide A stance and it permits some additional swivel wiggle for the thighs on the Y-axis as well. The wing assembly is also a little further to the rear which permits the Hi Metal to rotate the thigh leg up a bit more, without having to use the gerwalk joint.
In comparison, I feel the Yamato 1/60 VF1's feel like geriatrics when it comes to the leg articulation. The only way to get a half decent pose is to use the gerwalk joint ; which - imo - is like breaking a thigh bone in 2. Using the swivel at the knee to get the feet apart more, is also a pseudo kind of wide A stance.
I also agree with the anymoon review on the topic of the 1/60 head placement ; too high up. The Hi Metal does this a little bit better too.
The line was a bit overpriced, but the Hi Metal do indeed pose really nicely in scale to deluxe Transformers.