Three questions you should ask yourself:
1) Are you looking for a particular leather?
2) Are you looking for colourful/playful or conservative?
3) Do you prefer the slit card slots of the Citizen Twill or the standard card slots of the Copernic?
I find the Copernic has come in more leather choices over the past few years: Evercalf, Evercolor, Evergrain, Epsom, Alligator, Ostrich, Barenia. I have mostly seen Citizen Twills in fewer leather choices: Evergrain, Evercolor, Epsom, Swift although I haven't seen a Swift Citizen Twill in some time.
Over the past couple of years, the Copernic has had the "Jungle" and "Colorblock" models with bi-colour and multi-colour panels. Personally I don't like them but I'm sure it appeals to enough people for them to continue with the "Colourblock" models. I haven't seen the Jungle models recently and I expect them to be discontinued.
The Citizen Twill is often offered in far more colourful options than the Copernic (the "Colorblock" models aside). So if you are looking for fun/playful, the Citizen Twill would be my choice.
I'm not a fan of the slit pockets of the Citizen Twill but I do love the silk lining because it's far more playful while the Copernic would be my choice for a formal looking bi-fold.
I've never been a fan of the Poker or any money-clip wallet to be honest. I prefer using a separate money clip and cardholder if I don't want the bulk of a bi-fold wallet.
I hope this helps.
