Choice was dangerous: you had to forgo all other possibilities when you chose.

We Slytherins are brave, yes, but not stupid. For instance, given the choice, we will always choose to save our own necks.

We have to choose between what is right, and what is easy.

Where are you heading, if you’ve got the choice?” James lifted an invisible sword. “‘Gryffindor, where dwell the brave at heart!’ Like my dad.” Snape made a small, disparaging noise. James turned on him. “Got a problem with that?” “No,” said Snape, though his slight sneer said otherwise. “If you’d rather be brawny than brainy —” “Where’re you hoping to go, seeing as you’re neither?” interjected Sirius.

But if it matters to you, you'll be able to choose Gryffindor over Slytherin. The Sorting Hat takes your choice into account." "Really?" "It did for me," said Harry. He had never told any of his children that before, and he saw the wonder in Albus's face when he said it.