When in doubt remove it is my opinion. You can always add one later if you need. Personally I think their ugly and creepy and wouldn't want one in my system.
When the bristles are in big bunches like the picture above they are bad. Normally when they are smaller bunches like in the first pic they are beneficial scavengers that are ok to leave in the tank. Obviously I am sure there will be an exception to that rule but for the most part it is accurate. I look for a purplish color down the back for the good ones.