Does depend on the brackish tank! If you're doing mudskippers or an oyster reef with sort of marine-looking livestock, then bright white sand and clear water looks great. But if you're doing something more like a mangrove swamp or a brackish creek with bumblebee gobies, glassfish, archerfish and the like, then a more tea-coloured system will heighten the colours of those fish.
Cheers, Neale