The URL with the most accrued equity survives, because it carries the signal you most want to keep, and the other one 301s into it. Equity here means the things a URL has earned over time: backlinks pointing to it, ranking history, organic traffic, and the authority Google has built up around that exact address. When you fold two pages together, you want the survivor to be the one already holding the strongest hand, so the consolidation adds to a position of strength rather than abandoning it.
The reason comes down to what a redirect can and cannot do. A 301 passes signals from the retired URL to the survivor, but redirected equity is never a perfect, lossless transfer. So you keep the bigger pile intact on its own URL and route the smaller pile into it, rather than the reverse. If you instead kept the weaker URL and redirected the stronger one, you would be making your most valuable address the thing being redirected, sending your best equity through the lossy step on purpose.
There is one caveat worth weighing against raw numbers. Favor the URL whose address and structure also best fit the merged content’s intent. If the higher-equity page has a clean, descriptive, well-placed URL and the other is a buried or awkward one, the choice is easy. When the equity leader has a clumsy URL but the gap in equity is large, equity still usually wins, because that earned authority is harder to rebuild than a tidy slug. The judgment call is real only when equity is close.
Resist the instinct to keep the newer or prettier URL just because it looks cleaner or feels more current. Freshness and aesthetics are not equity, and choosing on those grounds throws away the signal you were trying to preserve. When you consolidate, identify which URL holds the most links, history, and traffic, confirm it also reasonably fits the merged intent, keep that one, and 301 the other into it.