Shinki run on a completely different architecture closer to PCs or Smartphones, and even possess BIOS functionality and SD Card support, while FA Girls have a modular plamo kit-based plug-and-play weapons and armor system and an Android OS-based launcher for its VR arena system. There is a small but intense third-party, underground scene for cross-platform duels between Angel Doll operators and Shinki/FA Girl masters despite the In-Universe rivalry between Angel Doll operators (who see Shinki and FA Girl Masters as lonely people who surround themselves with autonomous dolls to be surrogate daughters) and Shinki/FA Girl Masters (who scoff at Angel Doll operators for being jealous of not having a Shinki or FA Girl who can respond well to care and basically live alongside them in their daily lives outside of battle).
WMG / Busou Shinki
Rozen's Maidens are one of the ancestors of the ShinkiIf you've seen video footage from the Battle Rondo and Battle Masters tie-in games, Shinki have a 'core' where you must set three gemstones. This 'core', which does not exist in their direct descendants the Frame Arms Girls, is actually an artifical Rosa Mystica. Busou Shinki can never become Alice because they do not battle to the death and take each other's cores/Rosa Mystica.
The Busou Shinki Moon Angel OVA is a prequel to the Otomedius seriesThe human-sized Shinki-based combat gynoid chassis Kaguya and her sister Strarf MK2 were meant to serve as twinned processor nodes for is a predecessor to the human-sized Arnval and Strarf MK1 seen in the series proper - the design team was never able to perfect their creation(s) until captured Bacterian technology was offered to them, replacing the tiny Shinkis being used as their cores with Bacterian processor nodes.