Just like steak, the better the grade, the more you pay. What you are looking for primarily is cork that is as free of pits and dark spots as possible. I hold a personal bias towards the use of cork handles. This is especially important to me when I'm fishing in late fall through early spring when temps are below 50 degrees. Even when it's wet, I find cork to be extremely comfortable in hand.
Cork is easy to work with and maintain.
If it gets discolored you can clean it up with 0000 steel wool or a Scothcbrite pad, and it will look as good as new. Cork can be shaped easily without any special tools. Lathes and other tools make the job go faster and will undoubtedly produce more consistent results, but you don't need them to produce a well built, comfortable handle. If your handle is old and stained and full of nasty stuff such as oils, perspiration, fish attractants, or any other manner of other gunk that can easily contaminate it during the course of normal use, you will find that water on the handle will make it slippery and difficult to hold. Junk cork is a pain to deal with.