The model 5 is fine for the average user, the 6 is made for people who will use it often with thick gloves and it is made of a special metal that doesn't rust like regular steel will. I have a 5 with the hard sheath and belt clip for the hard sheath, I also wear it around my neck. I prefer the kydex sheath to the nylon, much easier to clean. All you do is flush it out, cleaning the nylon is a bit more involved.

The yellow is just to make it more noticable.