For years the OUA was the only CIS conference to wear full shields. In 2004, the OUA switched back to half-shields based on data showing that stick infractions (high-sticking, cross-checking) and other head-associated penalties (elbowing, I believe) were called more frequently in leagues with full shields as compared to leagues with half-shields, and that head injury rates were the same - if not slightly lower - in leagues with half-shields as compared to leagues with full shields.
I'm not sure if anyone tracked the penalty data since the OUA switched back to visors. However, having been involved in the OUA at the time of the switch, I can say the data was pretty compelling. Moreover, there is research showing that people perceive themselves (and others) as less susceptible to injury when wearing more equipment - and that this perception ironically leads to greater injury levels because these people do more idiotic things. One only needs to have played both rugby and football to know that this is true.