I
love playing piano, almost more than playing bass!
Piano is a fantastic instrument for getting a "complete picture" of the music. It's like a self-contained orchestra.
But IMO, bass is one of the most clearly and logically designed instruments for "seeing the theory". What I mean is, because bass is consistently tuned in 4ths, ALL fingerboard patterns are consistent in every key. I still have to think about how to finger a minor7(b5) chord in certain keys on the keyboard, but on bass I can play it instantly from any root.