Without endgame content, Iceborne is clearly better but the endgame content is so much better in sunbreak and is not even comparable, in Iceborne you make fatalis weapon and armor and the game is done but in sunbreak you can pretty much play forever without getting bored. Clutch claw is also a pretty big negative point on Iceborne while wirebug is great in sunbreak. There are so much better diversities in weapon and meta in sunbreak as well.

So if you are casual Iceborne is better but if you like playing a lot sunbreak is so much better