Yeah, get one for each set of characters. That is my attitude really.
Personally, I favor the ANH version, since day one, but TESB one is a fave in that it was more refined and geared for action (smaller helmets). I didn't like the lighter color of the silver/grey on the shoulders and the slightly lightened up brow (to make him less angry looking?) in ROTJ, but get why that was done.
I am not that fond of the ROTS look at all. Although I accept it is supposed to look like a NEW and immaculate suit...helm is too wide and TOO refined. That computer balanced face, where they sculpted one side, then let a computer lathe the other to match, where's the artistic expression in that!?!?! It's too perfect.
And Hayden, bless his heart, was just not quite big enough. But, that too makes sense for the story. he has to grow into it.
For a comparison between the helmets, look here:
https://web.ukonline.co.uk/bingo275/Tanonvader_helmcomps.htm
I will always prefer the 1977 costume since the head was so large and that brow, man, he was angry! That's why I made my own custom one (on a modified Sideshow body I might add...scroll down page) located here:
https://figuremasterles.tripod.com/id31.html
I made him because, whether ANH one is made or not, I've GOT to have one.
I guess that really, the rest is preference. Eye of the beholder stuff.
It's ALL Vader man! :chew
But, if SS made one or more, I'd get them all I guess. We'll see what is produced first. (I bet first up is TESB...why? not sure...guaranteed purchases maybe...or not... reverse that logic...put off the most in demand one til last...just a guess)