One thing with the full face mask is that you physically cannot dive. Firstly, the mask holds so much air that you are holding onto a balloon. Second, if you really force yourself down, your ears hurt a lot because there is no equalization. I tried to dive on a few of these, maybe two feet is good, five feet is painful.
Also, I ran a stablizing program on Linux. The super-expensive go-pro has built-in stabilization.
ps. on the day before we left a lady drowned snorkelling. She was on one of those jammed tourist boats, and nobody saw her. I suspect she may have had one of those 'deadly' full face masks.