I’m interested in these kinds of conversations because I have two young sons. Younger turns 4 in January. Older will be 6.5 then.
Older will switch to snowboard this season. He spent the last two winters (at 4.5 and 5.5) on skis (and the prior winter on toy cross-country skis in the back yard). I tortured myself about when to start him and whether to start on skis or snowboard. (I don’t really downhill ski -- I’ve only been about a dozen times. I do cross-country, though.) There were many factors in my decision-making. I’ll mention a few.
My main goal was to set him up for success and fun. Along those lines I bought into the physical-development arguments that say skiing first. (But I can see the point in the approach that says let the kid pick -- they’ll have the success/fun because they’re doing what they want.) (But I personally just hate to see people flail unsuccessfully at something and that was some of my fear with starting my kid on the board.)
I can appreciate what the OP is saying about stability. But the arguments against say that the *average* younger children don’t have the ankle strength and control to make the board do much of anything. (Plus their bodies are a lot less familiar with the toe-heel axis kind of balancing on the board compared to side-to-side balancing.) I’m just repeating the arguments here -- my sum experience is with exactly one kid, who hasn’t even switched to boarding yet.
I though older kid made great progress on skis. He spent 15+ days on the snow first season and 10+ the second. About half the days the first season were in full-day ski school. Second season he just had a couple hours of privates. (A teacher at the end of first season said kid was developing great and all he needed was miles under his belt.)
The decision to put him in ski school so much the first season came largely from a recognition of my own limitations and difficulties teaching close family members anything. (Plus the fact that I don’t actually ski.) Anyhow, it let me play more of the role of “let’s go explore” rather than “technique coach,” but I did insist that he ski his best, including a good bit of age-appropriate parallel skiing the second season. (I absolutely can’t stand watching small kids power wedging their way down a (steeper) hill on skis, whether they’re happy and in control or in terror and not.)
Also, when I was scouting all this out a couple of years ago, it seemed there weren’t many resorts that were offering a full-day riding program for kids as young as 4 (some only offered it to that age on weekends). Most of them wanted to put off riding until 6 or 7. My impression is that this seems to be changing, even in the past 2 years.
Regarding shitting their pants -- most schools make it real clear that even though they’ll take kids as young as 3 for all-day group lessons, the kids all need to be potty trained. This wasn’t an issue for my older son, but it will be an issue with younger.
I could write a lot more about this, but it’s already turning into a book.
I’m excited about getting older son on the board this year. I’m thinking of doing a private lesson for him the first day or two, then a handful of full-day group lessons -- but not go overboard like his first year on skis.
Younger son looks like he’ll be more of a challenge. Frankly, I don’t think he’s ready for it this season, but my wife (who skis) wants to get back out on the slopes this year.
Sooner or later your legs give way, you hit the ground.