From what I've read here:

We have a continuous spectrum with incrementalists on one side and completitionists on the other.

Incrementalists are claimed to be the realists ones. The have a pretty good idea of what is achievable. They consider the social, political, human and economic factors of the software development context.

Problems with them are they are short sighted. They do incremental little things that may add up and overwhelm them, creating unyielding messes.

Completitionists are claimed to be the dreamers, the idealists. They can see the big picture as an abstract mental model which needs to be perfectly complete and solved right.

Problem with them is that they struggle at doing things. Every little task has to be engineered to handle every single detail perfectly. Result, they never get things done.

As many people here, I think there are not 100% incrementalists or 100% completitionists. We can move to one or the other side of the spectrum depending on the situation. Incrementalists and completitionist are just constructs created to give an idea about the skills needed to confront different type of situations. I