I am far from an expert roaster but I have found that there are some beans, a batch of Sumatra I have at the moment, that I have only been able to get a darker (full city or full city plus) roast. Others do well at lighter to medium roasts (city, city plus). I drink it all, tend to use the darker roasts for espresso. The darker roast seem to have less acidity. It was just the idea that all the coffee OB tastes best when darker did not make sense to me. Having said that, I enjoyed most of the coffee I bought from them.