To me the new one looks about the same size as the MCU version, if anything slightly smaller.
i quite like the new helmet, works very well for ANAD Iron Man, and is great for other armoured minifigures. I'd say they they'll keep using the MCU helmet where they have to, like how they'll use the 2015 Batman cowl piece for the Justice League sets, but haven't been using it in Dimensions or The Lego Batman Movie.