PORTIA But this reasoning is not in the fashion to choose me a husband. O me, the word "choose"! I may neither choose who I would nor refuse who I dislike; so is the will of a living daughter curb'd by the will of a dead father. Is it not hard, Nerissa, that I cannot choose one, nor refuse none? (1.2.3)
Portia seems to resent the fact that she doesn't have a choice in her marriage. Though she doesn't say she would like to disobey her father's will, she clearly feels limited by the fact that he's snatched her choice away from her from beyond the grave. Again, we see that she's strong-willed enough to dislike her father's choice (so she's not a pushover), but she's generally a good girl. So, even though her father is dead, she won't defy his will.
PORTIA I am glad this parcel of wooers are so reasonable; for there is not one among them but I dote on his very absence, and I pray God grant them a fair departure. (1.2.15)
Portia has a ton of choices, but she doesn't like any of them. Her plight is similar to that of Penelope in the Odyssey. Like Portia, Penelope's suitors wanted her for all the wrong reasons. We do wonder, though, at the fact that Portia seems to hate all of the men for their character flaws, when the obvious reason to hate them is that they're trying to use her.
Does she not realize they're all after her money? Does she just not care? This will be important for whether she can love Bassanio, because he's also after her money.
Act 1, Scene 3
BASSANIO For the which, as I told you, Antonio shall be bound. SHYLOCK Antonio shall become bound, well. (1.3.2)
It seems Bassanio doesn't grasp the gravity of his choice to offer up Antonio as collateral for his debt, especially if Shylock is out for blood from the very beginning.
Act 2, Scene 2
LANCELOT "Budge," says the fiend. "Budge not," says my conscience. "Conscience," say I, you counsel well." "Fiend," say I, "you counsel well." To be rul'd by my conscience, I should stay with the Jew my master, who—God bless the mark!—is a kind of devil; and, to run away from the Jew, I should be ruled by the fiend, who—saving your reverence!—is the devil himself. Certainly the Jew is the very devil incarnation; and, in my conscience, my conscience is but a kind of hard conscience to offer to counsel me to stay with the Jew. The fiend gives the more friendly counsel. I will run, fiend; my heels are at your commandment; I will run. (2.2.1)
There's no evidence that Shylock is particularly awful to Lancelot—it seems that religious attitudes are at work in painting Shylock as the devil incarnate. He's caught between a rock and a hard place, as often happens in the play. Lancelot gives no reason for his choice; he just dismisses his conscience as a hard one, giving worse advice than the fiend.
This is particularly interesting when we think of the other person who must choose between Shylock and something else: Jessica. Though we never really see her reasoning, maybe Shakespeare is suggesting it was something similar to this?
Act 2, Scene 3
JESSICA Alack, what heinous sin is it in me To be asham'd to be my father's child! But though I am a daughter to his blood, I am not to his manners. O Lorenzo, If thou keep promise, I shall end this strife, Become a Christian and thy loving wife. (2.3.2)
Jessica chooses Lorenzo, and a Christian life, over her father and her Jewish background. She recognizes that it's a sin to be ashamed of her father, but she makes a choice that she thinks is truer to her nature. As her Jewish father's nature is so dissimilar to hers, it looks like her only choice is to become a Christian, walking away from being her father's child.
Act 2, Scene 7
PRINCE OF MOROCCO One of these three contains her heavenly picture. Is't like that lead contains her? 'Twere damnation To think so base a thought; it were too gross To rib her cerecloth in the obscure grave. Or shall I think in silver she's immur'd, Being ten times undervalued to tried gold? O sinful thought! Never so rich a gem Was set in worse than gold. They have in England A coin that bears the figure of an angel Stamp'd in gold; but that's insculp'd upon. But here an angel in a golden bed Lies all within. Deliver me the key; Here do I choose, and thrive I as I may! (2.7.2)
Morocco's reasoning isn't actually bad here: he compliments Portia by assuming no casket could hold her that did not reflect her worth. Still, he chooses wrong, if only because his values and expectations about love are different.
Act 3, Scene 1
SHYLOCK. Why there, there, there, there! A diamond gone, cost me two thousand ducats in Frankfort! The curse never fell upon our nation till now; I never felt it till now. Two thousand ducats in that, and other precious, precious jewels. I would my daughter were dead at my foot, and the jewels in her ear; would she were hears'd at my foot, and the ducats in her coffin! (3.1.8)
Shylock really dogs his daughter here, wishing she were dead at his feet so he could have his things back.
In one way, it seems clear that he loves his wealth more than he loves Jessica. But in another respect, Jessica has made her choice. Salerio and Solanio have reinforced that the girl thought herself to be unlike him and deserted him. She has made him the laughingstock of Venice and left him entirely alone.
Shylock too must make a choice. If he had been the sensitive kind of guy, Jessica might not have left him in the first place. Instead, he's got to piece his life back together, so he bemoans the one thing that can't actually desert him of its own accord. Money is all he's got left, so he chooses to focus on that rather than mourn the daughter who abandoned him.
Act 3, Scene 3
ANTONIO Well, jailer, on; pray God Bassanio come To see me pay his debt, and then I care not. (3.3.4)
Antonio recognizes that he has no choice but to resign himself to his fate. He no longer needs to scheme about being saved and can turn all of his attention to being loved and celebrated by his friend before he dies.
ANTONIO Hear me yet, good Shylock. SHYLOCK I'll have my bond. Speak not against my bond. (3.3.2)
Given the choice between mercy and vengeance, Shylock chooses the latter. What's more, his repetitious demand to have his "bond" demonstrates that he is completely inflexible, even after he is given ample opportunity to resolve his beef with Antonio in a peaceful manner.