Semper,
I'm not a medical expert and, unfortunately, there is not a scientific/medical study that will conclusively tell you which type or brand of head protection to buy. However, there are a few basic principles that can be applied when making your decision:
First, the energy of a baseball must go somewhere, so it is either deflected or absorbed. It seems to me that deflection is the best defense, so an angular cage is better than a flat cage. Most <acronym title='Hockey Style Mask '>HSM</acronym> have more angle than traditional facemasks, and consequently the <acronym title='Hockey Style Mask '>HSM</acronym> has a greater chance at deflecting the ball's energy.
Second, absorption is a question without any reliable testing. Are the Team Wendy pads superior to Wilson wrap around pads? I dunno. Team Wendy has conducted their own testing and THEIR results are impressive.
Umpire Ed Hickox has suffered as many serious head injuries as I've heard of, and the last I heard he is wearing an All Star <acronym title='Hockey Style Mask '>HSM</acronym> with a steel cage (steel is more absorbant than titanium). I also read a story recently about an NHL goalie who changed from titanium to a heavier steel cage after a head injury. It begs the question whether a heavy two pound steel facemask offers more protection than a one pound titanium cage.
Finally, I suffered a mild concussion earlier this year when I was hit in the jaw while wearing a traditional mask. I felt the effects for two weeks. I wonder if this blow (which wasn't really that severe) would have been reduced if I had been wearing a mouth guard to create distance between my jaw and skull (head of the condyle and glenoid fossa).
I hope this information is helpful in your decision making process.
Pete