Having never played Locomotion, I am wondering why I should buy the game instead of playing Open TTD. What are the main differences between the products?

On the highest gameplay level, Locomotion uses scenarios instead of always having randomly generated worlds (although some scenarios have random landscapes with pre-set conditions), and is objective-based instead of being a sandbox-like thing.

Thanks! Do you feel like there is enough content to warrant playing it instead? What I mostly enjoy about Open TTD is not the financial aspect, but rather the building up my own mini "model" railroad.

That is also possible in Locomotion, but you'll be too concentrated on the objective to do that.

Tell you what, try the demo and see if it's up your alley: https://www.gamefront.com/games/chris-sawyer-s-locomotion/file/chris-sawyer-s-locomotion-demo

Oh thanks, I was looking for a demo, but couldn't find one, that is perfect!

Personally, as I noted in my review, I think Locomotion is a worse Transport Tycoon.

The fleets are lacking in any real number, road vehicles are impractical to the point of non-existence, traffic control is non-existent as is routing, there's no way to maintain the fleet (so reliability is going to cast a shadow as you wait a decade for it's replacement.) and inflation rots the economy so hard that dollar amounts will seem as worthless yen by the time of the midgame, the landscape generation sucks, often creating landscapes which are not exactly pertinent to a transport game, you will be fighting cargo flow, and perhaps rather importantly click & drag building is missing.