In Arthur Miller's play, Death of a Salesman, Biff is the son that shows more concern for his father.
Willy Loman is a man struggling with a changing world. He lives his life in the past, remembering his greatly successful (and now deceased) brother Ben. Because Willy lives in the past, he believes that his son Biff has a life full of promise because he was a star player on the football field, but Biff is struggling to find a job; he failed math in his senior year, did not graduate and lost his college scholarship. Biff repeatedly tries to discuss his difficulties with his father, but Willy remains entrenched in his memories of happier days.
Willy is unrealistic about his importance in his sales job—from which he is ultimately fired because he is old—and the son of his old boss considers him a "dinosaur." Willy is quick to boast of how important he is:
WILLY: They laugh at me, heh? Go to Filene's, go to the Hub, go to Slattery's, Boston. Call out the name Willy Loman and see what happens! Big shot!
This, of course, is not the case. So it's not a surprise that Willy cannot face Biff's inability to excel in the business world, and resents Biff's desire to go out West and work with his hands in the outdoors.
In terms, then, of the son who shows more concern, perhaps we need to define the kind of concern each son displays. Happy acts like he is supportive of his father, but he is mostly concerned with his own life.
LINDA: Now that you get your spending money someplace else you don't trouble your mind with him.
HAPPY: But I gave you money last—
LINDA: Christmas time, fifty dollars!
And Happy and Willy's relationship is not mired down by Willy's delusions as is Biff's relationship with his dad.
Biff's wishes are a cause of constant friction between father and son, and they argue because Willy refuses to allow Biff to be what he wants, pushing him instead to work as Willy has. The constant tension and arguments might make Biff seem less loving, but in truth, he always comes home, and continually tries to make his dad happy with him.
BIFF [with reserve, but trying, trying]: [Oliver] always said he'd stake me. I'd like to go into business, so maybe I can take him up on it.
All Willy can do is dismiss Biff's efforts:
WILLY: What's wonderful about it?...Sporting goods?...He knows something about it! You know sporting goods better than Spalding, for God's sake!...Ah, you're counting your chickens again.
Willy's continual dismissal of his efforts breaks Biff's heart.
On the other hand, Happy is more concerned about doing what pleases him, including "womanizing." (His mom calls him a "philandering bum.") He is not the supportive son that Biff is. Biff continually attempts to please his dad, but Happy "plays around." Happy is also critical. When he finds out that his father has been attempting suicide, instead of showing concern, he gets angry:
How do you like that damned fool!
Happy then turns on his brother, finding fault for his failures. With his dad, Happy does not attempt to have a relationship with him; he plays a game to keep his father happy—coming up with empty dreams that feed his father's illusions:
HAPPY: We form two basketball teams...Two water-polo teams. We play each other. It's a million dollars' worth of publicity.
WILLY: That is a one-million-dollar idea!
Biff struggles with his father, but continues to try. Happy lives his life to suit himself. Biff is the better son.