Why were the Triarii differently equipped?

[Corvus]

Max, as far as i know, the association of Apulo-Corinthian helmets with the triarii is just a reenactorism.

I think you are right, its just that also a lot of Illustrations to this subject show them with the helmet.
What helmet would they wear instead? Except montefortino of course. Were Greek helmets and armor popular during the 4-3 centuries BC?

I don't think it offered any more protection than a montefortino. In fact, I suspect that the eye-holes, which were often left open, would be something of a weak point. In contrast, the shape of the montefortino is better suited to deflecting thrusts and encouraging slashes to glance off.

Yes, that's what I also think, the A-C Helmet seems pretty unpractical.
And I cant understand why soldiers would prefer something "fancy" above something practical like a montefortino helmet.