BC -
One of the beautiful things about the speypages / forum is that you will get a lot of perspectives from a lot of people, all valid in their own way. Yet it's important to understand that many of the responses come from the perspective of a certain preference or style that the responder subscribes to, and you'd do well to investigate all of these to find which are best for you.
Here are a few things I would offer to this discussion:
1) A rod does not cast a tip, a line casts a tip:
First and foremost, a rod does not cast a tip. The line casts the tip - and if the rod can cast said line, then the rod is 'good for the tip'. Yes, of course there are considerations for moving a sunk line that conveys to the action of the rod, but I wanted to establish that the relationship between a tip and the rod is through the line, not direct from rod to tip.
IMHO, the notion that rods are suitable or not for tips is hogwash, however rods are suitable or not for lines. In field tests on the Snoqualmie River last Saturday, I consistently threw the Windcutter 7/8/9 with a 15ft high density head to the backing with the Solstice Series IM8 14'3" 7/8wt 4pc using a relatively easy stroke, letting the flex and recovery of the rod to do the work - not my arms. It is a balance between a flexing taper and a super-high modulus graphite and works equally well with a light greased line method or an abrupt fat head with grains to chuck provided the caster allows the rod to do the throwing, not the arms. In fact I have been casting for several hours a day for over two weeks and my body is none the worse for wear, the rod takes the beating for me.
2) Using the arms verses using the rod:
Where one approach is to muscle a tip out of the water, the other is to use a deeper flex in the rod to lift the tip with it's recovery.
Case in point: Circle spey verses snap-T
It's universally accepted that the circle spey is a far more effective method of lifting a tip out of the water than the more direct pull of the linear snap-T, although the two casts only differ by a very small distinction. The circle uses a slower, fuller, more circular path putting a wider bend into the whole rod blank. That tells us something important about moving weight.
When opening a heavy door, like an industrial swinging warehouse door, we can either "hit it" to open it or push it open with a constant accelerating motion. My hand hurts just thinking about option #1.
In my humble opinion, relying on rod stiffness instead of flex and high-modulus recovery puts the onus on the arms and shoulders, not the rod to achieve the same task. I am no physics professor but it's intuitively obvious to me that the direct pulling method would be more effectively performed with stand up tuna gear than a long spey rod, because it uses direct leverage instead of rod loading and unloading. Ok that's a little over the top but you get the idea. The spey rod provides a tool for doing appropriate movements like the circle spey that are efficient, pleasant, and deadly for fishing deep.
3) Preferences:
I am a caster, not a rod designer but I find rods with light tips and heavy butts to emphasize the use of the arms more when casting. Here is specifically what I mean by this (voiced in the context of my own preference, of course):
Given a simple switch cast:
a) a soft tip gives in during the lift and sideways transition into the d-loop sweep, so the start of the cast feels mushy. Thus the arms pull harder and faster to try to feel the load happening, which finally comes later as you get deeper down the blank. By the time you have a good sense of load in the hands you've come around quite far and it's time to stop to form the d-loop, otherwise you will push too hard to the back or over-rotate due to the late feedback. So the next time you sweep back more quickly to feel the load coming back.
I find a stiff tip combined with the proper flex profile (Spey action specific) further down the blank provides good feedback at the critical point in the transition from the lift to the sweep, "out in front". This allows the d-loop to be a very relaxed and consistent movement that is largely performed by the rod, not the casters arm force trying to feel the start-up load. To answer your question about CND, this is a characteristic that I find most appealing about the CND taper.
My theory (right or wrong) is that without this start-up feedback (e.g. soft tip), the brain tells the arms pull harder to compensate for the lack of feel, speeding up the sweep of the d-loop dangerously close to the point where it should be stopped to allow the 'dee' to float back smoothly. Maybe this is why people call the rod "faster", because the sweep back has to be fast to compensate for the lack of initial feel. I can speak for myself in this case, that is what I feel.
Preference again: I find the smoothness and feel in the sweep while forming the d-loop to be a most enjoyable part of spey casting and thus much prefer a less radical taper.
IMHO, either rod design will deliver a beautiful forward cast by adjusting the angle of attack approriately and doing the right thing in terms of tracking and acceleration.
So it boils down to whether you're fast-muscle twitcher or a smooth operator, and each and every one of us are different so viva la' difference!
4) Rod speed verses line speed
Since my rod only moves 10-15 ft and that is all counted at the tip, I don't understand how speed relates to a rod. I hold onto the rod but I cast a line therefore I believe the designation of rod speed (whether "fast" rod or "slow") for rods is nebulous at best. Line speed, however makes all the sense in the world to me. If anyone can explain what rod speed is all about I would sure appreciate it. I need to get more enlightened on the topic by Nobuo but for me it's all about taper and stiffness, and stiffness relates to line weight and grains. So it's down to just taper and since that doesn't move I don't know how to relate that to rod "speed".
Enough of my exercise in rhetoric already, my point is the terms "fast" and "slow" are fuzzy, and line speed is where it's at.
When I want line speed, I want a rod (taper) that gives me (a) the biggest wad of energy (b) released with the greatest rate of acceleration (c) in the most focused shape. To me the optimal configuration is the rod that flexes appropriately to build up the maximum potential energy in a high-quality material that unleashes this beast in a manner that is easy to focus during the split-second that I get to do it in. My dream rod is the one I don't have to push very hard at all to get tremendous line speed for full distance.
5) Fishing / fighting taper
One of the comments often heard about light tip / heavy butt rods is that they are not fun for fighting fish. The exertion of pressure on the fish goes from not pulling hard enough to pulling too hard quickly back and forth throughout the fight. Hence this lack of "connection" you spoke of.
I prefer a more traditional flex for fighting fish as well. In the end, the objective is to cast easily, accurately, pleasantly - and catch fish.
Summary:
This is a matter of preference and taste, and all opinions are valid to the beholder.
Both designs are great and should be checked out. It's great that we can have lots of choices to enhance our Spey fishing lifestyles!