Rimworld is simplified in some ways in that you have only one z level, and it comes with more QoL features.

Rimworld is a lot easier than DF to learn, and more intuitive.

And generally, you have fewer rimworld pawns than DF dwarves, so managing them is easier.

I for one love both games. Sometimes I want the simplicity of Rimworld. Other times I crave the endless complexity of DF and all the possibilities it brings.

it's the better video game IMO. Even after the steam release of DF, Rimworld is a lot more approachable and has more player direction (including multiple end goals). Dwarf fortress isn't trying to compete as a video game, though, it's doing its own thing as a dwarf sim that you just so happen to be able to play. I've incidentally learned so much about metallurgy because of needing to look up what black bronze is and what I need to fit my dwarves in some cool armor

Personally I like Rimworld with mods better than Dwarf Fortress. Dwarf Fortress is really good but Rimworld has a better ui. In Rimworld the graphics are more fluid and complex. For example many things that happen in Rimworld are represented with graphics (i.e. a pawn on fire, a pawn missing an eyeball, a pawn not wearing a shirt in -80c weather). Understanding what's going on takes a lot less effort. Rimworld also has really good mod support. That C# and Harmony thing they have going on means literally anything that can possibly be thought of can be modded in.

My other reason for why I think Rimworld is better is a personal preference, but I like sci-fi better than medieval fantasy. I like being able to proliferate lasers and machine guns and nukes so I can completely destroy my enemies and be the one who gets the last laugh. I'd say the biggest factor for why I have over 3000 hours in Rimworld is because I was always grinding for that glorious moment when I can finally unleash squads of cyborg supersoldier space marines all over the world, send orbital nukes at all the population centers and laugh while all the now-helpless tribals and pirates that had been harassing me for hundreds of hours finally get what's coming and can do nothing but watch in horror as a well-deserved apocalypse unfolds. It's judgement day, motherfuckers.

Dwarf Fortress is a fully 3D world, and simulates a helluva lot more stuff. It's also fantasy, while RimWorld is sci-fi.

But RimWorld is (more) moddable, and potentially could be Dwarf Fortress and more. You can add and change things in DF, but not mechanics so it is quite limiting in what you could do with it besides playing. RimWorld can be turned into a completely different game if one was so inclined.

Similar but also different in many ways. One thing is that you can override your pawns' automatic actions with manual things and even queue actions up. Also, no z-levels (unless you use a mod, which actually works decently).

It's not centered around digging/mining, it's mostly collecting resources and building freestanding structures.

I didn't really get into Rimworld until recently after ~100 hours or so in the Steam version of DF, but it has completely sucked me in. Tons of amazing mods as well.

It's really an incredible game with unlimited replayability.

With Dwarf Fortress, I find I can only play a dwarf fortress, so to speak. It's hard for me to do things truly different from playthrough to playthrough.

Rimworld, especially with its DLC, gives you way more options. The Biotech DLC for example enables you to make different fantasy-races. From the way your colonists look to their abilities to their strengths and weaknesses. Have a look at the four available DLC on the wiki. https://rimworldwiki.com/wiki/Downloadable_content And not to mention all those mods. So many mods.

There are countless different ways to create a scenario of your choosing.