I use the Kick's GT .690. I like it an awful lot. I did not experiment with any other tubes, but once I shot it I don't think I need to. My local gunsmith/dealer is very well known around here for his hunting talk shows and general knowledge about the sport. He was bragging about his shot patterns on a weekly call-in show, so I had to drive over there to see what he was so excited about. His patterns were very good, but had nothing over mine at 40-50 yards. I've been pleased.
Good Luck.