Andrew Lincoln's close up shows you how far him and his group will be pushed in the upcoming season. It also portrays his character very well and shows that he may take another trip or two to Crazy town as he did in season 3.
On the flip side, Daryl's portrait displays a rather darker side of him, based upon the cold gaze he has in his eyes.The writers have truly done a wonderful job exhibiting Daryl's backstory throughout the seasons. For example in season two, while searching for Sofia, Daryl and Andrea had a conversation about how Daryl got lost in the woods for two weeks without anyone missing him. We also know that Daryl was abused as an adolescent, the writers first hinted this in season two when Carol bent down to give Daryl a kiss and he flinched, they later revealed the scars on Daryl's back in season three.
My prediction is that this season, we're going to see a completely different side of Dixon, a mad at the world type of attitude. According to Reedus, Daryl seems to be more mad and hungry for revenge on The Governor than anything.
In an interview with Examiner, Reedus quoted, "He wants a ferocious revenge, he doesn't just want to see justice -- he wants to rip his head off."
I honestly hope that in the end, Daryl is the one that takes out The Governor. Daryl is the only one who has lost blood at the hands of The Governor, that in its self is why I believe he deserves the honor to end The Governor.