I like the ones with "file' texture, where when you move them in and out they "file" out some of the tobacco, this helps prevent the tobacco from expanding back where the hole you created was and plugging the cigar back up.

Some sort of centering would be good, but once you use a draw tool a few times I think you're not very likely to poke a hole through the side of a cigar, at least I haven't after the first few times I used a draw tool (knock on wood).