Here's my stance on the ROTS Vader vs. ESB/ROTJ Vader issue.
I don't mind symmetry. If there's going to be a Vader cameo in Rogue One or another OT era spin-off, I want a symmetrical helmet. An asymmetrical helmet likely wouldn't stand up as well to scrutiny as a symmetrical helmet would. Furthermore, an asymmetrical helmet likely dictates a lesser number of close up, head-on shots, in order to avoid drawing attention towards the asymmetrical structure of the helmet. In the OT, the best shots involving Vader are from an angle or some distance away. What I don't like about the ROTS helmet is how large the helmet/dome appears in relation to the mask and the rest of the body; ROTS Vader always looked as though he had an oversized head to me. In addition, I dislike the flat lenses.
On the subject of how the rest of the suit compares to those seen in the OT, I agree with others in that I believe it should look like a less refined version of the ANH suit. For example, the robes should be placed over the upper chest armor, as in ANH. I do not mind, however, the fact that the chest armor is connected to the shoulder plates, or that the control panel on his chest is embedded into the bodysuit rather than attached via straps, as is the case in the OT. In my eyes, Vader would tinker with the suit over the years, modifying it in order to make it more comfortable and easier to move in. I could very well see him having the shoulder plates and the upper chest armor separated in order to make the movement of his arms easier. On the subject of the chest plate, having it embedded in the suit itself would likely result in Vader having difficulty bending forward, and I could easily imagine Vader changing that in order to make bending forward easier.
