Cub Scout is sitting on Central Brain (each minion here has +1 power). If another player's 3 power minion moves to the Central Brain, is it destroyed?
1. Cub Scout says "After another player's minion moves here..." so move is resolved, Cub Scout checks the minion's power, destroys it?
2. "If multiple effects would happen at the same time, the player whose turn it is chooses the order." The current player taking their turn decides if it lives or dies?
Wow within 1 week 3 questions to the nature of this issue have been asked. I guess this question specifically wasn't asked so I'll address it.
Okay first a disclaimer. The answer to this question is directly tied to the nature of what "after" means when it's on a minion. This has never been directly addressed by the developers that I've seen so I'm goint to answer based on what I've pieced together from related thins they've answered.
Cub scout reads:
Cub Scout: Ongoing: After another player's minion moves here, if it has less power than this minion destroy it.
Cub Scout's ability says AFTER... (yada yada yada). Hence cub Scout is forced to give the other minion the benefit of any power benefits that might kick in first. The ability of the Central Brain does not have "After" thus it gets to trump the Cub Scout's ability and happens first and the thing about starting player getting to pick which ability gets to resolve first is not invoked.
The most obvious place you can see this is on the Leprechaun which actually explicitly states (resolve it's ability first). Oh and to pre-empt anyone who might try this although Cub Scout's ability does not say "resolve it's ability first" like Leprechaun's does you'll notice that the text for the Leprechaun appears in parenthesis which I interpret to mean it's a clarification and not a limitation.