Hey Doug,
There's a bunch to know regarding DIR. Do you have all the links yet?
As for neoprene drysuits, I went from a neoprene drysuit to a Viking to my Abyss. I don't like full neoprene drysuits for the following reasons:
They tend to be stiffer and less flexible than a well fitting shell suit.
They are considerably more buoyant.
They lose their insulation value as you descend.
You can't adjust the insulation.
I believe these are also the DIR arguments against them too. I just don't like them compared to a shell suit, and I routinely dive in water temps less than 40F for up to 90mins at a time.
As for the fins, overhead guys like the Jets and Turtles due to their small size, good efficiency and propulsion, ease of using multiple kick styles, and they kick up less silt than long fins.
Take care.
Mike