nesting dingies vs inflatable kayaks as tenders
"Are there other factors I''m missing?"
A couple. How will the tender be used, and where? I guess some folks will be happy with anything but I would find a kayak a poor tender substitute if the boat is being cruised, the dink is the family car, reprovisioning must occasionally be done, the mate was other than a mermaid, and the weather was seasonal and water cold vs. tropically stable and warm.
I liked your list and think you''ve got the issues re: the nesting dink pretty well identified. It will present an obstruction for you, both visually and when working the foredeck, and IMO they are a better answer when they can be placed on the cabin top aft of the mast. They can also be terribly frustrating to ''nest'' in a chop, when the two pieces are bobbing around in different directions and you''re trying to drive bolts. Dave Gerr''s Nature of Boats offers what seems like a suitable method for attaching dinks but there are others, too. If that''s the direction you go, don''t over look this issue.
You''re right about the project; it''s good fun and easy. And building a nesting dink is even easier because the work footprint you need is small, the pieces are lighter you are working with, etc. The Two Paws looks nice...but as you say, there is a tradeoff between freeboard when it''s a dink and visual sightlines when it''s on deck.
Portabotes don''t appeal to me but perhaps you should consider that alternative before making a final decision. And it''s possible to inflate a simple/cheaper inflatable on a foredeck your size (e.g. one of the venerable Redcrests or Redstarts by Avon; they should be available used for not much money). As you inflate the front half, you just move it forward and up onto the lifeline/pulpit (one side or the other) while inflating the stern. But of course this option won''t sail and won''t row well; it just offers other benefits (stability, load carrying, small footprint & weight deflated, easy to repair).
Good luck. Fill us in on how the dink will be used, and where - perhaps that will stimulate other comments.