It depends. Do you want to really challenge your brain. If you do I would get brain age as it has sudoko puzzles which are very good.
Brain Academy is more of a diversion for the younger market.
Big Brain.
It's much more of a game than Brain Age.
And Nurikabe shits on Sudoku.
0922 - Puzzle Series Vol. 11 - Nurikabe (J)(Legacy)
Big Brain Academy lacked very much in challenge. I played for one day on training and nearly gold ranked all of the missions. Not fun.