I like the Catch a Key minigame more, partially because I have issues with my touchpad where sometimes I accidentally double-click when I try to click once and it makes the Shock a Lock game frustrating.
I'll still play both of them, however. Starting in Zafaria or Avalon, those Silver Chests become quite rewarding.
I don't mind which game I get when I open a silver chest. I'm just excited to see what the rewards are. I never pass up on a silver chest, because they often give really useful and harder to obtain reagents like sunstone. This is only the case in higher worlds like Zafaria/Avalon and up... Possibly Celestia. Never leave a silver chest behind!
I love the catch a key game. I don't mind the shock-a-lock.. I just wish they would put more stuff in them.. I think it would awesomer if they had a chance at crown armor, pets, permanent spells or just some crowns...