I like a ski without a lot of sidecut. At first you may need to get used to the slow initiation of a carve, but skis made for big ass turns are a blast. I can't speak specifically for ON3P, but I can say that its definitely not a drawback to have a big turning radius.
Well I was talking about pow ski's yeah, because the OP is talking about pow ski's too..
With: ''in 3-D snow there are a lot more factors than the sidecut of the ski.'' You mean that there are more factors that influences the turning of a ski? Offcourse there are a lot more, especially in the powder (real 3-D, groomers are more 2-D)
1. How much is the turn radius function of design ;
I remember watching a line video where pollard was explaining hooking in pow in reference to why they developed early taper. I remember dynastar back in the day made a big thing of their intermediate skis being really easy to initiate carves because they basically had "late taper" Obviously they didn't call it that, but essentially the ski got wider through the tip up past the contact point to make turning easier for beginners.
That was kind of a tangent, I would say that turn radius is a major part of the design of a ski. All other features aside, turn radius is maybe the determining factor in what kind of turns the ski wants to make naturally. Can you make a large radius turn with a slalom ski? Yes. Could you make it through a slalom course with 210 cm straight skis? Sure. But obvioiusly the goal is that you match the ski that you choose as best you can with the type of skier that you are and the type of terrain you ride most. But, maybe you ski a certain way because of the skis you are on currently. Does it mean that you would dislike something different? no.
2. Is the turn radius calculated consistently?
I would think so. But put 5 company's 180 cm skis next to each other and I guess you could assume the same differences in "actual" turn radius. Especially since some skis have elliptical sidecut, so who knows how you calculate that.
Actually not really.
By skiing forward and bending the ski along it's length, you shorten the radius. The more forward pressure, the smaller turns you can crank out without breaking edge grip.
Case in point- I had a pair of 183 BROs a while back that had I believe a 37m radius, but by getting and staying forward onthem and turning by driving the tips and keeping that energy in the ski I could bang out little tiny <10m SL turns on them without just throwing them sideways.
The turning radius number just basically tells you how big of mountains and terrain they're built to take on, it's by no means a concrete number you cannot change nor is it a limiting factor to the turns you can make on them. That is wholly dependent on your skiing.