Re: how does each part of the taper affect line behavior?
Are you looking for more distance or are you having turn over problems? What I write below is just my general take on a wide range of thoughts when it comes to todays huge selection of lines.
By now you may have figured out that I'm pretty set in my ways. When ever I walk the path through the jungle of manufacturers and marketers I keep an eye on what has been working for years and watch out for traps. I have never fished for redfish but I do a little surf fishing every year and I use the same lines that are on the rods for river fishing. Looking at the SA & Airflo specs I can't imagine them preforming very differently. If the caster were digitally recorded and then the two videos were superimposed over one another the computer generated results may show some difference in the way the lines unfurl but this (for me) wouldn't prove too much. I would have to assume that the caster was perfect in exerting the same line speed and delivery with the different lines and therein lies the problem.
When we are talking about casting a fly line some things do matter. For instance greater distances may be achieved when using heavier lines and rods to deliver flies of a certain payload range. Tapers such as WF may deliver better shooting capabilities when used by casters who are adept at double haul casts and shooting the line. The use of a stripping basket will even the playing field for the guy who is using the DT line and his shooting ability will go up because of the free line in the basket. This discussion can of course go on and on.
My take on lines is that I would not trouble myself wondering if one with a rear taper 3 feet longer than another would improve my cast or its distance. Since I am stubborn I would fish with what ever line I currently own and continue to do so until I found that each time out I caught nothing while all those around me were killing them because they had one of the specialized fly lines. The only time I have ever had this experience the issue was that I needed to adapt to using Hi Density sinking tips and tungsten leaders in order to achieve the proper depth to reach the fish. If you run into depth problems then you've gotta change your system but for general casting with floating lines I don't get caught up in hair splitting.
I know that what I say smacks of opinion laced bullheadedness but I have found it to be true for too many years to ignore it.