About four years ago, after encountering cracking on Cortland flylines, I switched to Rio, and have been very pleased with the performance and wearability. The lines that I have used are the Striper intermediate and Striper sinktips. The tapers load the rod and turnover heavy flies quite nicely. They shoot well with minimal tangling in the shooting basket, if a little water is left in the basket for lubrication. Cracking has been non-existent.
All my flylines, including freshwater, are now Rio. I believe their R&D in coatings and tapers makes them the benchmark for flylines.