I did build of both these kits at the same time. Cause of the similarity of the inner frame on both of these kits. The legs have some slightly different parts added on to them. But for the most part outside of the color pieces the legs share a bit of pieces in common.
Front and Back:
The crotch section uses the same base part for its construction on both the RG Freedom and Justice.
The upper body also uses the same base under frame as well. But that is about all they share in common and same with the arms.
Headless and armless Justice and Freedom.
Both kits took me a little bit cause I was building them at the same time. But they also share the same shield and beam rifle. The back packs are obviously massively different. All in all the builds of both are not that bad.