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The number on the box is only the starting point. Two units of identical rating can behave very differently beneath a graphics card that jumps from 100W to 500W in a fraction of a millisecond, and describing that behaviour is what the ATX 3.1 specification exists for: a compliant unit must absorb excursions to double its rating without dropping the rail or firing its own protection.
The rest of the decision is what appears on the side label and in the cable bag. Look for a single 12V rail, a modular layout that matches your case depth, and the exact connector types your graphics card asks for. Everything beyond that is packaging.