Having seen some very nasty crashes with skiers taken out by boarders I have to say I am very wary around them and make an effort to ski where they are not.
The problem, IMO, is mostly confined to snowboarders who don’t ski and skiers who don’t snowboard (and idiots generally).
If you do both, it’s easier to anticipate the likely movements of the other.
Too many times I’ve seen people riding and a skier try to pass on his blind side right as he’s about to turn into it. Snowboarder doesn’t look and turns right into skier. Snowboarder at fault, but the skier could have probably avoided it. You might not want to (or feel that you should have to), but a bit like driving, i’d rather give way to an idiot than stand my ground and get injured.
Also, depending on conditions, it’s harder to have a “planned” turn on a snowboard, so turns can be more erratic. Again, a wider berth would be advisable.
My pet hate on skis is snowboarders changing direction without looking (it’s not that hard is it??), especially when they decide to cut right across the piste.
My pet hate on a snowboard is skiers getting too damn close (particularly on narrow cat tracks when you’re just sitting on an edge and need to get a turn in but there’s some goon coasting alongside you inches away)