The only real difference between a coffee mug and a Bierstein is size. I prefer drinking beer out of an open container over drinking it from the bottle because I like breathing it in while I drink. That DOES make a difference. I also want something that is taste neutral like clay or glass because I want to taste my beer and nothing else. Everything else, size or shape of the container is really up to personal preference and has no actual effect in the real world. However, just like I want my steak nicely prepared on a plate I want my beer nicely poured in a glass. It has no actual measurable effect but it pleases my mind so I do it anyways. "Das Auge trinkt mit."