I use the first three lines extensivly in NZ. The MPX has a 5 ft front taper and the Infinity a 7 ft front taper, i.e they are both not 7 ft as stated. The MPX has more weight up front and having a shorter front taper is a better line for turning over large dry flies - e.g. hoppers and cicadas - on long leaders. It is a fantastic NZ backcountry line. The Infinity does not have the same grunt, but presentation with small to medium flies is better. It also casts further, as it has a longer head, and is better at mending at distance. The Infinity is a great general purpose line for fast action rods. The trout is a lovely line with incredible presentation at all distances when using smaller dries and lightly weighted nymphs. Having a reverse taper it loads quicker and can deal with more weight and more wind, without sacrificing presentation, than other presentation lines out there, i.e. those with very long front tapers (e.g. triangle taper or delta taper profiles).