Roman helmets: Imperial Gallic/Italic and Ridge - comparisons and sources

[CaesarAugustus]

The reason for change of equipment is not necesarily because the
new model is better/stronger, but because the type of warfare and the type of enemy is changing.
The Ridge helmet seems to offer more freedom of head movement and would be probably better suited for
the climate in Syrua and Messopotamia.
The Romans always adopted the armor and weapons of their enemies. Fashion is also an important factor.

Yes and no. Or, better, this is a bit of a contradiction. Probably, one of the reasons for improving the protection of the gallic helmet was to face the parthian arrows. So cheek protection improved and so on. 

For what we know, Romans already knew the ridge helmet, that was already used by Parthian/Sasanians, but Romans did not immediately adopt it. 

Was the adoption related to logistic reasons, regardless the effectiveness and strength of the helmet?