Not an easy question to answer. There are skis like the LINE Afterbangs which are plain old soft and noodley, but that's not necessarily conducive to being the best for buttering since you might just flex them till your face is in the snow. Then you have something like the surface no-times which are really stiff but have a rockered tip so you can get a bitchin' pop out of your butter, but tail butters are almost impossible. Skis are like recurve bows: a bow that is really soft is easy to draw but doesn't have any power, and a stiff bow is harder to draw but is more accurate and powerful. If its too stiff, you can't draw it at all and its useless. So a really soft ski is easy to flex but will feel practically dead, and a ski with a stiff flex and complex construction will be more difficult to bend, but when you do its very rewarding.