Advantage to the ring for me is several things. When cutting the tippet off the leader, be it to add fresh, or to add a different weight, there is no chance of clipping the leader. I tried the loop to loop, but it hinged for me. Plus I use fluoro for tippet and it has cut my thread leaders.
As for the Tenkara, I do attach a ring to some, but only by request. I make Tenkara lines for several people and some do mot want the ring. They say it makes it harder to attach the line to the rod.