[joe_star]

Mainly the breadth and volume of content (good and bad) available.

Also route creation and editing is a big one for me

[QJ-6811]

There is so much available for OpenRails (and ex. MSTS), I think everyone can find their favorite locomotive, era and routes.
Personally my preference is that you can personalize and adjust as much as possible to your own preferences.
With other SIMs it "works as it is" and in most cases you cannot merge anything.
It is not without reason that it has been "my train SIM" for 14 years....! :)

[captain82]

I think because Open Rails is still in a "developmental phase" that there's no real limit to how far we can take things. Remember when the first rendition of the PRR route was released and how taxing it was on MSTS whereas ORTS barely breaks a sweat LOL. But compared to all other sims out like TSC and TSW which rely heavily on graphics ( however cartoonish TSC) and licensing, not to mention having to purchase other routes you'll probably never use just for its assets. ORTS with the right minds tinkering on it will undoubtably surpass any and all. OpenBVE probably being second.

[steved]

Ease of modification.
I can get OR to do what I want it to.
And a 24 year investment in content and knowledge.

Randy