> with the first style, productivity is constant at best—getting things together in the first place is a struggle, and then adding features or fixing bugs continues to be a struggle. On the other hand, the second style of project is even more of a struggle at first, but once it works it's like magic: new features are easier to add than you'd expect, and I've had way more things work after my first attempt than anyone has a right to expect.
I would like to challenge that by pointing out that not a single piece of large software (except maybe a compiler or two) has ever been written using the skills/concepts of the higher levels of this chart. What you say may be true if generalized to better upfront design etc., but there's also no evidence that this is better done using the approaches discussed. It's not even about measuring productivity; it's about arguing over the properties of an empty set. When it comes to small (> it's because I'm willing to put effort up front for a long-term reward.
You're equating upfront effort with a particular choice of technique, and one that has never been put to the test.