It took me months to learn how to do an ollie and I practiced every day. But I managed to land my first 360 on skis first try and got them down comfortably after a few days, then at the end of last season started doing them off medium sized park jumps and even got the 540 down in the last few days, as well as 450s when at the start I'd literally never hit anything harder than a tube and never slid right to the end. So from my perspective skateboarding tricks are much harder than ski tricks.
Feel free to disagree but I think an ollie is technically a very complicated trick with many more things going on that a simple 360 in the air on skis. What tricks do you think are equivalent difficulty wise between skiing and skateboarding?