I think as a footballer Davies is a better player. Serge has way more talent but no idea how to use it so Davies is the preferred player because despite his vast limitations at least he understands the game. Ideally though both would be upgraded on as neither is close to good enough.
I also think that Davies would be much easier to coach because although he limits what you can do, if you put him in a specific role (one that has zero ball playing or offensive responsibility and minimizes the space he has to cover defensively) you know that he can and will go out and do that. With Serge you can make all the plans in the world and he will just go out and do whatever the hell he wants, which is usually the dumbest thing possible.
