The Phanteks G400A is the objective winner of this comparison, securing five category wins against the single victory held by the NZXT H510 Flow. The most impactful advantage for the Phanteks G400A is its inclusion of fans, which provides a 100% improvement over the competition. While the NZXT H510 Flow offers a 50% advantage in 3.5" drive bay capacity, it fails to match the overall hardware superiority demonstrated by the Phanteks G400A across the majority of measured specifications.

Users prioritizing out-of-the-box cooling performance should choose the Phanteks G400A, as it provides double the number of included fans compared to the alternative. Conversely, the NZXT H510 Flow is the better selection for builders who require higher storage density, specifically those who need the additional 3.5" drive bays for their system configuration. Select the Phanteks G400A for superior fan utility or the NZXT H510 Flow if your primary requirement is expanded internal storage capacity.