I find the Extremes to have way lower rolling resistance compared to W240's, which must be the all-time worst rolling tyre Nokian ever made. Now with Extremes existing in 622, there is little reason in my opinion to buy new W240's, except on some bikes the width difference. I'm not going to throw my W240's away, though.
In any kind of actual snow Extreme and W240 perform much better than the other studded tyres which only seem to have tread for the looks.