Answer: In my opinon, Teamlab Borderless was better than Teamlab Planets, and more worth it for the money.
I spent four hours in Teamlab Borderless exploring every exhibit and having tea at their En Tea room (¥500, $4.50 extra). Borderless has a huge variety and number of immersive art experiences. Its open concept means you are free to wander to every exhibit, and go back to your favorites.
To compare, I spent one hour inside Teamlab Planets, because there are fewer exhibits, and only one path that everyone follows. Note you cannot backtrack at Teamlab Planets.
I thought the exhibits were more impressive at Teamlab Borderless, including my favorite Forest of Resonating Lamps. At Teamlab Planets, the main exhibit where you are up to your knees in water and surrounded by mirrors, was a unique experience. However, for a central exhibit at Teamlab Planets it was not as impressive or visually appealing as the main Teamlab Borderless exhibits.