Since this category of sight is BUIS - with optics as the primary - why not the Magpul MBUS? They've been redesigned with a smaller rear sight footprint, are durable, don't lose their anodizing and shine up, come in colors for better camo, and can be lighter. Price leaves room for other stuff, too.
If combat durability is a priority, the GI FSB and rear sight would be first choice. I'm not much on paying extra for billet machining when I know it has a high markup for the utility value it serves.