Have you played Orbiter? How is it?

[Klapaucius]

I got into KSP because I was drafted to help run an afterschool program for high-school kids using KSP as a way to get an intuitive grasp of very basic orbital mechanics. 

I'm wondering if Orbiter Space Flight Simulator would also be a good option--both for teaching and just for personal gaming. I saw this article which peaked my interest.   Before I spend a few dozen hours with tutorials and noodling around trying to learn it, I'd be interested to hear from others who have played it what they think, and how it compares to KSP.

[Canopus]

It's a lot more tedious. I got into Orbiter after playing KSP which helped me because i already knew the basics of orbital maneuvers. But other than in Kerbal Space Program i don't think you can learn the mechanism of Orbiter through actually playing the game. I spent a lot of time reading manuals and watching tutorials to understand the Multifunction displays and their uses, and after flying a few missions to the Moon, Mars and a big one to Jupiter and its moons Io and Europa, i basically lost interest in the Game. I'm glad i spent time with it though, seeing as it was part of the inspiration for KSP, but i can't see me returning to playing it very soon.

I wouldn't recommend it as a teaching tool, but i would recommend you to try it out for yourself.

[NSEP]

KSP focuses more on the game aspect, it simplifies many things, making it playable, but at the same time, losing its realism. Yes, we do have Realism Overhaul, but Realism Overhaul isn't the most simple and stable thing ever.

Orbiter on the other hand focuses more on the simulator aspect. Orbiter isn't much fun to play as a game, but is a usefull tool for Space Agencies to simulate their launches, as seen here.

KSP is an educational game for kids and Orbiter is training software for Astronauts. Pick a side.