갖추다 = get the necessary equipment, wardrobe, personnel, etc. in place.   It emphasizes not lacking what's necessary.

준비하다 = prepare something in anticipation of something.  It emphasizes the action and the result of the preparation.

e.g.

- 저희 호텔은 200개의 객실을 갖추고 있습니다 = Our hotel has 200 guest rooms available.

- 이번 행사를 위해 재미있는 프로그램을 준비했습니다 = We've gone and created a fun program for this event.

Hello! It should be... "What is the difference between...."

갖추다 - possess - (ownership) or (control) having a complete power over (spirit)

준비하다 - prepare - make something ready

Examples:

He possesses the ability to control time. (ownership)

He was possessed by a demon. (having a complete power over)

Thanos prepares to conquer the universe.