Neither of those strategies work against competent players. When I see a Deoxys Speed, I switch to my Shed Shell Wonder Guarder that I always have on hand. Well, one of the two of them. That MMX is really weak until it gets in a Belly Drum, making it easy to kill. However, I have been experimenting with a Deoxys Speed that is actually good against good players in the meta.
Deoxys-Speed @ Assault Vest
Ability: Klutz
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Timid Nature
IVs: 30 HP
- Trick
- Taunt
- Destiny Bond
- Parting Shot
This is a fun set because people see a Deoxys Speed and they switch to their Wonder Guarder. Well, most defensive/support Wonder Guarders really don't like to have an Assault Vest. Also, after they have an Assault Vest, they no longer have a Shed Shell, so they are potentially easier to Perish Trap. Now that brings me to my next set, a Perish Trapping Aerodactyl.
Aerodactyl-Mega @ Aerodactylite
Ability: Shadow Tag
EVs: 252 HP / 252 Atk / 252 Def / 252 SpA / 252 SpD / 252 Spe
Jolly Nature
IVs: 30 HP
- Soak / King's Shield
- Encore
- Perish Song
- Heal Order / Disable
This set is designed to trap Pokemon that think they can't be trapped. However, depending on what kind of Pokemon you want to trap, you have to run different moves. If you want to trap Ghosts, you can run Soak (it removes the Ghost typing and replaces it with Water, as opposed to adding it). However, by running the combination of King's Shield (or Spiky Shield, but KS is more useful IMO) and Disable, you can block a lot of switching attempts with Volt Switch/U-Turn. If you think they're going to do one of those moves, you can use Protect, and then Disable, possibly and then Perish Song.