I've not had much success with looped lines & leaders. For me, they seem to generate wind knots, and tangles more that tied connections. I cut off the loop and use knots to secure the fly line to the leader.
The marketing ads say that you can change your leader out quickly, but how many times does that really happen? Usually a tied leader will last me about 2 weeks before it becomes too short and I need to change it out.
But, there may be those who like the looped lines. I do have to admit that a looped line is easier to change out, in lieu of tying a nail knot or an Albright knot, but I've never had such knots to fail on me. It seems to me that a tied connection turns the fly over readily, as opposed to a "loose" connection.