First, anyone commenting on the use of a helmet, who has never at least tried one, for one full game, is like someone who doesn't vote, complaining about how the country is being run. Talk to the hand !
With that said, here is a web page that describes in detail the differences between using a Helmet and a Mask;
http://www.reegind.com/helmet.htm
Now, I think there are two reasons why eventually everyone will be wearing a helmet;
1) Technically, it 'is' supperior to a cap and mask (see the web page). Those who demand equipment that gives them the best performance, will / have switched.
2) [keep in mind, I am not a lawyer, just my opinion here] Eventually, insurance companies will drive the requirement. I believe the reduction (or perceived reduction) in injuries will speak for itself. And to top it off, I think once everyone is wearing a helmet, they won't be required to take it off to make calls (as part of the safety ruling). Taking it off to make a call is all for show. It is absolutely NOT necessary. I also think that those hold-out associations that are stuck in the mudd, and won't allow umpires to wear them, will eventually get sued by an umpire who gets hurt wearing a mask that they did not want to wear, and being required to remove it to make calls.
Yes, I wear a helmet, and wouldn't step out onto the field without it. Fortunately, it is not held against me by my association, or fellow members. Performance is all they care about from any member. Change is tough. Good or bad, it can be difficult for people to accept.
Think about this: If helmets had come before masks, no one would think helmets look stupid. They would think the 'new' mask does.