As it relates to the Ocean Reef Neptune (this is the Ocean Reef section)....
Some problems with true fullface masks are:
1) If you loose your air supply by either an equipment malfunction or empty cylinder, you have to take the mask off to use an alternate air source.
2) They make you more buoyant.
3) Some designs will be prone to higher breathing gas consumption.
4) You surface and you are still breathing your cylinder down and you can't talk to anyone without taking the mask off.
5) You can't always use a different regulator than the one that is attached.
6) Some people complain that they are heavy.
1- Correct. Part of the training is to take off the mask and switch to an alternative supply. You should also carry a mask with you. Just in case.
2 and 3 - Probably true, but haven't noticed much difference.
4- Incorrect. They have a "surface air knob" on the side that you open up to let fresh air in. This stops tank air from being used. What happens when you leave the knob open and submerge? You can calmly close the valve while continuing to breath, not a big deal. You CAN talk at the surface, but it is really muffled.
5- From the Ocean Reef Neptune website: •Optional accessory: Special adaptor allowing for connection of several kinds of regulators (two adaptor sizes, medium (standard) and small)
6- See 2 and 3. I can only speak for myself and the Dive Team, but haven't heard any complaints about the weight with the Ocean Reef Masks. Our old FFM systems, on the other hand....
Some of the good things:
1) Your face stays warmer.
2) It is more difficult to drown when wearing a fullface mask.
3) They are less prone to leaking at teh face seal like a standard scuba mask will.
4) If you get the hang of it you can talk with the various communications systems (OTS is the best, get a bone speaker).
1 - Correct- OH HECK YES!!!! You may have to cut up your hood to get it to work right with the Full Face Mask.
2 - Correct- If you passed out, you'd still be able to breathe.
3- Correct - Or more correctly, a little leak is no big deal. On a training dive, after a mask replacement exersize, my wife was complaining about her breathing being "a little wet". I checked her mask, and she had a strap stuck under the face seal near her chin. The water was POURING in (I could see it), and it was just "a little wet".
4- Correct - It definately takes getting used to.
I'll also add:
5 - Kinda goes along with 2. When the FFM is on, and adjusted properly, it is virtually impossible to accidentally get it knocked off. If someone were to kick you in the face, you'd be more likely to break your neck than loose your ability to breathe (like when you get a regulator knocked out of your mouth).
6 - With your nose and mouth at the same pressure in a Full Face Mask, I think that it is easier to clear your sinuses as you go down. The clearing mechanism can be a hassle, especially if it isn't adjusted right, but I think the whole clearing process is easier. Just my opinion.