At my age I am all thumbs so I prefer to use the RIO Gold or RIO Grand trout lines. I like the loop to loop connection at both ends and especially at the leader connection. It is alot easier IMHO to change leaders on the water than fooling with knots. Just works for me. I checked the RIO site out and see one reason for using the "Mainstream" line... price. I have used the braided system and like that as well a long as you put a drop of glue on the braid.
Different strokes for different folks.