I would say Stardew isn't really super centered around the dungeon crawling elements although you tend to dungeon crawl a lot while RF4 depending on how you play can be pretty combat intensive. Depending on your taste, RF4 features might be a con if you are not used to the JRPG genre since it can be difficult to clear bosses/mobs(there is an easy mode though IIRC). Stardew combat is more 1 dimensional while RF4 has different weapons different spells and different teammates that can diversify your playing experience. RF4 has also a lot of JRPG elements with combat and complex crafting system with you being able to invite up to 2 people/pets to go outside town and beat monster/bosses up while Stardew is more akin to dungeon crawling to mine or gather monster loots for crafting. Also I want to mention, Stardew has gay marriage while RF4 does not but in RF4 you can pseudo gay marriage with a setting later on. Stardew in comparison is more akin to traditonal story of seasons towns(granted I do not play all), with them having different dialogue options depending on how close you are to them and town isn't as alive as RF4 but characters do move around. Sometimes they would give you stuff or invite you out which adds a lot charm to the game. Also in RF4, the town tend to me more livelier and not lifeless thanks to the fact villagers move around town and them greeting you everytime they walk past you. They generally have better personalities and a more diverse dialogues. In terms of characters, RF4 blew Stardew out of the water IMO. Stardew is liked a lot because of how it refined the farming game genre while being a huge nostalgia to a lot people. RF4 has a main story while stardew doesn't really have one.
Stardew offers of a more traditional life farming simulation with a dash of dungeon crawling while RF4 is more like a JRPG with farming elements depends on how you play it. I be comparing unmodded Stardew and I would not be comparing graphics since one is pixel one is 2.5D that is a bit dated. Depends on how you play it, both of them can be pretty relaxing and charming but Stardew players from what I've seen tend to have opinions on how Stardew can be more stressful early game.
As somebody who played both, I would say it really depends on your taste. I think its better to ask it in subs like r/patientgamers. I mean you are in a rune factory sub lol, so the majority of the answer will be obvious.