I dive with an Ocean Reef Neptune Nira II, I use a maximus regulator on it, altho they offer one of their own. They have this model and one new one called the Space. There are many advantages to FFM, and some disadvantages... Other good FFM's are the AGA , Kirby Morgan EXO setup. Most do not cover your ears, unless you go full helmet style.
Advantages:
Little to no Jaw fatigue
No dry mouth
Ability to add communications (pricey but worth it if u need it)
Ability to add drinking bladder (no do not fill it with booze !)
Better view of the whats outside of your mask
Very NICE for cold water diving !!!!!!!
Great if you have to dive in contanimated water, protects you.
Always get the surface valve option and quick disconnect !!! very helpful to have on any FFM.
Disadvantages:
You must get TRAINED !!! or be a very skilled diver to use !!!!
You should carry a backup mask as a just in case. And practice ALOT with ditching and switching.
If you are OOA, you have to ditch your mask, unless you have a setup to have a 2nd reg on the mask (which I can do) or a valve setup that kicks you over to a different tank (which I think is better solution)
Cost - You get what you pay for, but in my opinion a FFM is worth it's price.