Most people say snowboarding is harder on day 1, then gets easier to get better at. Skiing is much easier on day 1, but will be more of a challenge to pick up skill. This is just due to the nature of being able to stand up and using the lift. Being on two separate skis is much closer to natural than being strapped in to a single (mostly) rigid board.

That's just to get to intermediate level. Both are probably equally difficult to get very good at.

As someone who's mediocre at both, I would agree with the first thought.