I liked collecting items and fighting wild Pokemon there.
I preferred the Battle Dome myself because the tournament setting was great and Tucker as the Frontier Brain was awesome. I thought he was easy to beat.
I wish we could've actually captured the wild Pokemon that were found in the Battle Pyramid facility and at the Battle Tube though, or at least keep the items.
The Battle Pyramid and Battle Pike were my favorites. I liked the unpredictability and adventure aspects.
The Pike's reliance on luck to get around is exactly why I didn't like it; I have no luck and always ended up struggling.