兄が社交的なのに引き換え、弟はとても無口だ。
Unlike his sociable older brother, the younger brother is very quiet.
に対して is a more general contrast marker, while に引き換え often carries a stronger sense of unexpected or striking difference.
一方で simply states two contrasting facts; に引き換え emphasizes a subjective contrast, often with an evaluative tone.
Standard kanji spelling for this contrastive expression.
Variant kanji spelling using 替; less common but still seen.
Derived from the verb 引き換える (to exchange), literally meaning 'in exchange for', which developed into a contrastive expression.