Hi,
No comparison, really
Reflex sights give a sight image focused at infinity that stays on target even when you move your eye relative to the sight.
With an iron sight, you have to bring your eye to a very precise position and keep it there, and you can only focus on either the sight or on the target. If you focus on the target in order not to lose it, it becomes even more difficult to keep the eye in the correct position.
It would easily be possible to design another "arm" for the attachment ring that carries iron sights designed as primary sights. You could also put commercially available iron sights on the standard arm - it's NATO rail, after all However, iron sights for reason of ergonomy and accuracy require a fairly long "sight radius", and are best placed as far forward as possible.
I'd also use some kind of crosshairs or ring-and-bead arrangement to make the sight easier to read than the tube. Additionally, to be really accurate, the arm would need some adjustment mechanism (which the current design doesn't have, as the reflex sight is adjustable).
Quick draft:
View attachment 654742 View attachment 654743
And in the end, you really save only 30 EUR, 132 g of weight, and one Lithium battery that lasts years in normal use, while dealing with a much less convenient set of sights.
Regards,
Henning