For some reason I did not like the bottom part of Darth Vader’s mask. It looked like a flexible rubber pull over to me. And Vader’s walking stride (gate) was noticeably different. Also the voice seems to have been processed quite differently as well.
I agree with your observation of his mask and thought it stuck out like a sore thumb. But, after pulling up some images from the OT, it seems very similar to this go around. I think what was going on in the OT is how he wore his cape. If you look at a few different scenes, often times his cape was covering a good portion of his chin/neck. Also, I think lighting had a lot to do with it. Im with you though, it still bugged me.
In the original Star Wars Vader’s helmet goes from down over the top part of his eye goggles when he’s talking to Leia on the Tantive IV to way further back on his forehead when he’s in his TIE Fighter later on.