The vf-1 is my favorite valk, vf-1s focker type specifically. The skull 001 is the flagship of macross. I love the minimalist style of the vf-1!
My second... definitely the yf-19. Looks very extreme and agressive in all 3 modes.
The yf-21 is my third favorite, a true big bad boy. I love the gamlin's vf-22 color scheme.
Personally I don't like the sv-51 very much, but yes, in gerwalk mode is one of the best. Looks very organic, like a dark nasty bird.
Kawamori is going into a more realistic style I guess. He's the best mecha designer, second to Kazutaka Miyatake of course.