I think the key difference to me (as someone who enjoys both) is that Rimworld is more interesting from a moment to moment standpoint, the sheer depth of simulation in Dwarf Fortress produces far more memorable events.
Put another way, I don't remember any specific events in Rimworld, but I'm more than happy to tell you about the dwarf who pathologically elected to engrave the walls of the fortress exclusively with depictions of a particularly delicious piece of cheese he ate.
I have read about a dwarf that engraved pictures of rats (and just rats) on a particular room. Turns out he disliked the noble the bedroom belonged to, and that noble was afraid of rats.
Put another way, I don't remember any specific events in Rimworld, but I'm more than happy to tell you about the dwarf who pathologically elected to engrave the walls of the fortress exclusively with depictions of a particularly delicious piece of cheese he ate.