For Joes, I'd say I prefer removable helmets. Especially after seeing most of them bare-headed in the cartoons and comics. It depends how it's done -- if a removable helmet makes their head look too big with it on, I'd rather have a sculpted helmet-head so they look cooler in action (which is how they'd be used most).

Cobra troop-types, I'm less bothered. The DTC Cobra Troopers, Snow Serpents and Range Vipers are cool for their helmets/masks but really if they'd not had that feature it wouldn't have been any great loss. The individual characters again can have a bit of depth from having a more "casual" look but moulded helmets, masks, etc do give them a harder edge and make them more scary if you can't see their vulnerable, "human" faces.

I'd imagine the main issue people have with Munitia is that having a permanent hat stops her looking like Mistress Armada from the comics despite pretty much copying her colour scheme. I'm more annoyed that this implies Hasbro had no intention of doing a "proper" Armada figure, which also throws doubt on the possibility of other DDP characters. If they were even going to release any more figures at all...!