Can narrower inside of gate valve reduce pressure by losses?
The bronze valve will offer a lower pressure drop to the flow of water as the path has fewer changes of direction or changes in diameter.
The diagram for the plastic valve shows a 90 degree change in direction, then the flow is constricted through an orifice, then a further 90 degree change of direction.
Using the plastic valve when the flow rate and therefore velocity is low won’t be too serious like a low flow drip feed watering system but if the flow rate needs to be higher, shower or filling a bath then the losses may well cause an issue.