I don't wreck the infrastructure, the planet is usually fully developed and running at a profit immediately after I invade, not to mention providing conveniently located forward basing/shipbuilding facilities.

To keep the infrastructure, you have to be careful how you invade.

I would rather take out the planet quickly in a military game.

And sometimes I find the infrastructure is wacky. No factories.
Mainly tanning salons and tatoo parlors;)

Unless you are trying to minimize micromanagement, why destroy any newly taken planet? With a bit of effort, you can easily make it profitable and/or useful to your empire. More population = more research, income, production, ships, or whatever you build it to do. I never eradicate any planet.

I play gigantic maps too, although never with "abundant everything," and I have a tendency to role-play much more than think about my score.

The only time I ever went on a scorched-earth binge was when I had been managing an already painfully large empire and one of the AIs (the Torians, IIRC) pulled a couple of grievously annoying moves that caused me to decide they and everything they'd ever built needed destroying.



I'm also into diplo wins at the moment, and this point makes me wonder how (if?) the AIs think of the player destrying freshly conquered colonies. I haven't noticed an AI scorching earth, and it seems like the behavior should make your diplo ratings "not so much fly as plummet."

Just hit the destroy colony button in the planet interface. You can even do this to your homeworld.