I've done both and consider myself an "expert" in both. Double blacks, trees, chutes etc. Not much park though. But I picked up snowboarding day 1, heel/toe fakie. Skiing, I picked up pretty quick, not quite as quick.
There's different things that are harder. I found that the small park I do was easier on a board. Where a board was harder through trees. Skiing switch for me was harder than fakie on a snowboard. I might be an odd case, but I found skiing to be more of a challenge. And also more enjoyable.