Gakitsuki had the ability to alter his appearance such as taking on a human or fly guise.
Ravenator had no other form of him was ever shown.
Gakitsuki went inside Seikai's stomach to hide. Never had any association with Burai or Kou.
Ravenator hid inside a sandwich that Tommy was eating in order to get inside his stomach to make him eat without end. No conflicts with Tideus or any of the Alien Rangers were ever made.
Gakitsuki made Seikai grow giant sized.
Ravenator never made Tommy grow giant.
Gakitsuki escaped when Seikai resisted eating Tsuruhime in the guise of a burger.
Ravenator escaped when Tommy resisted eating a giant sundae.