The be quiet! Dark Base Pro 901 is the objective winner of this comparison, securing victories in six out of eight evaluated categories. Its most significant advantage lies in its storage capacity, offering 150% more 2.5" bays than the alternative. This superior hardware density makes it the more robust choice for users requiring extensive internal drive support and a higher overall feature set across the majority of the measured specifications.

The Phanteks G400A is the preferred option for budget-conscious builders, as it holds a 72% advantage in MSRP compared to the be quiet! Dark Base Pro 901. Users who prioritize cost efficiency over maximum storage expansion should select the Phanteks G400A. Conversely, those who require the extensive drive mounting capabilities and the broader range of technical features provided by the be quiet! Dark Base Pro 901 should choose that model instead.