I've been trying to take in this issue of wide and narrow skis, harder, faster,...etc.
When using PMTS movements my experience tells me you can create angles at both slow and high speeds. Given that the wider boards natural turn radius is longer than their skinnier counterparts, the narrow ski makes skiing shorter turns natural to that ski side cut much easier. Using the same angles created by tipping and counter, the longer boards will turn vary nicely also within their natural turn radius directed by their sidecut. Whatever ski, narrow or wide, I believe skiing with the body centered letting the feet work under you, is key to solid turns in all terrain at any speed with any ski.
The wider and longer skis certainly may need a bit more motion to get going because there is more resistance with more surface. Now if you're skiing INSIDE the natural turning radius of that ski...in otherwords shortening up those turns, for sure the wider ski is going to be more work in (did I put enough anti-persperiant on) more work, certainly more work than the narrower skis. But cruising within the natural radius of that ski..tip, lift, and counter...stay centered, keep your hands in sight, just dance baby, dance, the feet is where the magic is.
Still, it's is much easier for beginners through intermediates to make turns on skis in the 63-68mm waist.? But turning is turning...ya got the skills, skiing with most skis under 95mm waist can be be tipped edge to edge just as easily with those who have the skills,.... at slow speeds as well as wipe the tears out your eyes speeds.
Just one mans opinion,
Gary