The tax-free growth advantage compounds dramatically over time. A modest S&P 500 investment from a decade ago would have nearly quadrupled in value. The real difference emerges at withdrawal, where a taxable account surrenders roughly 15% to capital gains taxes while a Roth account preserves every dollar. That difference doesn't just represent savings-it represents money that stays invested and continues compounding in your favor, creating a widening gap between the two account types over decades.