The Security Industry Association has released a marketing study that examines user, dealer and integrator preferences to learning about and evaluating new products and purchasing decisions (see 51 page report here).
For manufacturers, it's likely worth scanning through, as it has numerous charts and rankings.
One thing I found funny was the conclusion that print trade magazines are the dominant source of professional information (with 81% saying that they regularly read them, compared to less than 50% said they read the trade mag online versions). However, at the end, in the methodology section, they disclosed that respondents were selected from 9 security trade magazines, which obviously explained that conclusion. Of course, it's hard for anyone to figure out where people overall get their information in that it is inherently skewed by how respondents are selected.
Another interesting point was that LinkedIn came in 3rd for information choices, beating out suppler / manufacturer websites, which makes no sense to me. Supplier websites, as a whole, are most certainly to me the most impactful category of information, given their brands, depth of material on their sites, etc.
There's a bunch of other stats, on trade shows, demo preferences, switching products, new production selection, etc. (see 51 page report here)