For a budget helmet the new Black Series Darth Vader is great. The dome can be easily lifted off its magnetic mounts to reveal the detailed mask below, and this can also be lifted off - with a loud hissing sound - leaving the neck and chin sections for the classic "Billy Joel with a harmonica" look of Sebastian Shaw in Return of the Jedi, and pressing the snall button on the side of the neck results in a great breathing/gasping/coughing audio loop. It's also detailed inside.
The mask is a little wider than the EFX PCR, and the dome a little smaller, but it's a pretty good size overall. The photos below show the Hasbro on the left and the EFX on the right.
I'm currently planning on modifying it a little, such as replacing the plastic ESB style tusks with aluminium RotJ versions, and adding gunmetal paint to the mask, but will leave it as is for now.