Well visually i prefer Phanton Ganon because he looks more powerfull than Bongo Bongo. After all bongo bongo looks hanging headlong (i didn't know that two words before write this, be here was a great idea.) so he looks prisoner, but still being darker. And Ganondorf and Ganon... well, ganon doesn't fly and ganon less the mask
I'd choose twinroba to because for me was the most original mecanic for a boss in the game, and the funny history beside was part of my decision to.
And finally i'd choose morpha by the same reason of firedri, i like challenges and in it's times was my most hard battle in the game.
Bongo Bongo was fun. Probably my second favourite.