Carbons are designed and manufactured for different purposes, there are more than 100 kinds of them. Almost all revolve around LP and and VP operation. They are dependant on the original raw material, i.e., bitum, coconut shell, wood, Lignite etc and the grain size and shape. Larger grain sizes are for VP and smaller for LP.
Bitum can be used for either, so it mostly a grain size thing. CS is mostly for VP and Wood and Lignite are mostly for LP. Large pellets, like the Kent, were designed for VP operation and especially pellet carbons. It is no that they don't work they will, they just are not very efficient. Kent's pellet carbon is just a selling gimmick and that is all it is.
Most carbon from the actual manufacture come with a data sheet or you can get one. That data sheet and its carbon parameters. i.e., Iodine #, Molasses #, mesh size, ash etc, etc, tell all about that carbon.
What is the deal with grain size ? Air has little density or mass and is a "gas" and is easily diverted, such would be the case with small grain size, as the air finds a way around the carbon more. Water is much more dense, with more mass, so it is not as easily diverted, thus smaller grain size.
We want to try to stay a least 8 mesh or smaller. Meaning 12 mesh is smaller in grain size than 8 mesh. 8 mesh = 2.38 mm. For us, it is quite often smaller than 10 mesh. In general for LP the smaller the grain size the better it is. However, when it gets to small it becomes very user unfriendly. Imagine a carbon that is 100 mesh or 0.149 mm. About the smallest we go for our application is 12-40 mesh. Meaning the carbon has a range in grain size of 12- 40 mesh and most prefer more like 12-20 mesh or even 10 -20 mesh.