Your best stage in this matchup is Dreamland. The low ceilings are great for combos, the tri-platform layout benefits you more than him, and Whispy can mess with his banana ledge traps. Lylat is also a good pick, specifically because of the last point. It is quite tough for Diddy to set up banana on ledge with the fluctuation of the stage. Not to mention, Bayo is much better at recovering safely without getting, as they say, "Lylated" than Diddy.
On the other side of the coin, Final Destination is your worst bet. Diddy is great at walling you out, so the lack of platforms really hurt. The high ceiling and no platforms hurt combos immensely. If the Diddy is playing an optimal, patient game, running a game back is quite difficult on FD. Also, though this may just be me, I feel that Smashville is Bayo's second-worst stage in this matchup. The single platform yields similar problems as on FD, and he can use it better than you. Diddy even has a tricky technique on the moving platform: repetitively down tilting, locking you in place. If you feel comfortable on it, however, it still is an acceptable pick.
The stages I didn't specifically mention (Town and City and Battlefield) are fairly even. Unless you choose to go Smashville, one of these two stages will likely be your starter. After game 1, ban FD if you won, or choose DL or Lylat (whichever wasn't banned) as your counterpick.
Bayonetta
On the other side of the coin, Final Destination is your worst bet. Diddy is great at walling you out, so the lack of platforms really hurt. The high ceiling and no platforms hurt combos immensely. If the Diddy is playing an optimal, patient game, running a game back is quite difficult on FD. Also, though this may just be me, I feel that Smashville is Bayo's second-worst stage in this matchup. The single platform yields similar problems as on FD, and he can use it better than you. Diddy even has a tricky technique on the moving platform: repetitively down tilting, locking you in place. If you feel comfortable on it, however, it still is an acceptable pick.
The stages I didn't specifically mention (Town and City and Battlefield) are fairly even. Unless you choose to go Smashville, one of these two stages will likely be your starter. After game 1, ban FD if you won, or choose DL or Lylat (whichever wasn't banned) as your counterpick.