Here's an example to help you understand how cylinders work in 3D programs:
![Image](http://i1202.photobucket.com/albums/bb365/Andy_Hack/MX%20Simulator/CylinderComparision_zpsebf1ntlv.png)
Looking from the side every cylinder looks obviously pretty much the same, you cant really judge a difference when a texture is applied later ingame.
When it comes to the top of a cylinder its the opposite, now its obvious that the cylinder isnt a perfect circle, the edges are clearly visible.
However, even when you see both viewports you see a nice looking pipe, but also how many edges the cylinder has...
In your case, i think 6-8 is the way to go. I hope this helps you understand this whole cylinder thing a bit better
![Smile :)](./images/smilies/icon_smile.gif)