they're also the entity that gives "bite" (pun intended) to the pollution mechanic, which complicates lots of tradeoffs in the game. with biters/pollution, trees are both an inconvenience and a helpful pollution buffer. it's not trivial to decide whether to build your starter base in the open desert or nested between forests. additionally, the tradeoffs between solar vs steam and the effect modules are shallower when you ignore pollution.

I understand some people just aren't really into the tower defense side of factorio. that's okay, and it's a good thing that the settings can be adjusted to suit a wide range of playstyles. but if that's you, I'd recommend at least trying a low pollution / efficiency-focused playthrough. the game gives you a lot of tools to manage pollution, and the biter threat can be pretty minimal if you use them. imo this preserves the balance better than just turning off biters.

I rarely defend. Factorio is a great example of a good offense being the best defense. Just take out any biter camp that comes close to the edge of your pollution cloud, and you never really have to bother with defense.

> the game gives you a lot of tools to manage pollution

The popular Krastorio 2 mod adds even more: wind turbines from the start, more efficient ways to produce energy between steam and nuclear, and it even has air purifiers that reduce pollution. That's almost cheating. On top of that, taking out biter camps is a lot easier with the anti-material rifle.

There's a lot of important details in this : when, how and where biters expand, how much less killing settlers rather than nests increases evolution, &c.

Good point. I often play train worlds and the normal settings there is to not have biters expand at all. I often change that to having them expand slowly, but much more slowly than they normally do. Having new biter camps pop up in your cloud will require some defense of course.