Bottom of the Helmet, Open or Closed?

I've seen it done both ways, but what is "correct"? An open bottom helmet with a neck liner? Or a "sleeve" bottom type helmet?

Does it matter?

Which is cooler/easier to wear... also gotta consider voice amplification as needed...

Your thoughts please.

JP in Atlanta

Boba's is open w/ the neck seal going up into the helmet. Jango's is closed I believe

yeah, i believe the boba's have neck seals and jango has the jumpsuit plus the stretch fabric enclosure on the bottom of the helmet