Haven't used cinnamon in beer but I have used it in cider and have used it for cooking quite a lot. I would think that sticks would yield better and more controllable flavor with less trub. I would definitely suggest that you soak the sticks in vodka for a few minutes to sanitize them before introducing them to your beer. No telling what kinds of yeastie/beasties might be hiding on or in those sticks!
In cider I use 1 stick per gallon. It gives just the faintest hint of cinnamon. It would seem logical to me that beer would take more than that because the flavors in beer are so much more pronounced than in cider.