Now, this is quite interesting...
The contests vary from the original R&S ones, to the super contests in D,P&Pt, to the contest spectaculars in OR&AS, the pokéathlon is in solely in HG&SS. Aesthetically speaking, I prefer the ribbons over the pokéathlon medals, however pokéathlon contests base themselves off mini-games, which are indeed very entertaining, but will be painful if your game is emulated. The R&S contests revolve mostly around the pokéblocks and movesets, and I remember often having difficulties in contests due to opponents often managing to traumatize my fellows. Some players didn't enjoy much the original contests, and the developers also thought of replacing the contest halls in emerald with the battle tents. In D,P&Pt the contests include also dressing your pokémon fellow (take your fave pokémon from the Sinnoh pokédex and put sunglasses like Ash's squirtle's... yup, you get the idea :P ), after showing your accessorized pokémon to the public one gets to guide them through a dancing round and end it with an acting comptetition similar to the one in R&S, except your pokémon won't get startled and there's a new "three judges mechanic"
┻━┻ミ\(≧ロ≦\)
Unown team, at least I can make text with it :P
RSE secret base or DPPt secret base?
EDIT: I wonder if it's two options only? I had something else I was hoping to type down...