Slitherine

Which one to pick ?

And what is that thing highlighted

That's the weapons range. Which one to pick depends on other factors such as cost, etc.

I always go for the 17cm. That extra range keeps it functional longer with fewer turns wasted on movement. It also keeps it out of range of opponents artillery which means less RP wasted on reinforcements.

17cm is a fantastic counter-battery asset because of its long range. Best artillery piece for Germany until you get to Hummel in my opinion.

For me, range is the best possible stat for artillery. Not having to waste turns moving makes an artillery gun much more useful than a piece that hits harder but ultimately fires half the time compared to the longer range one.

The 17cm K 18 outranges every artillery unit in the game, except for the Krupp railway gun. The incredible range far outweighed the one extra damage of the 21cm, in my opinion. Enemy artillery will be helpless.