Pretty sure you can't just walk into any random a.ss store and trade a PS4 game.
Also, I'm pretty sure that a person can only trade in a game once regardless of what console it is for. If someone trades a game in, obviously they no longer have possession of the game meaning that they can't trade it in again.
I mean trading in general.
Example: i trade the game to my homeboy, then he one day gives the game to his little brother, then one day lil bro sells it on eBay...etc
the PS4 game holds more value than a X1 game b/c the PS4 game doesn't LOCK after a # of owners (from what we know at the moment).