Horses for courses I reckon. Have one of each at the moment and I find myself reaching for the hardtail for the weekday arvo ride - which is all about 60-90 minutes of workout on fairly tame local trails. The hardtail eats it, but you still need to make smarter line choices to avoid getting too beat up. Admittedly it’s a 27.5+ Chameleon, so the 2.8” tyres definitely take the edge off the bumps. It’s also a shitload of fun to ride.
Never really felt the need to use the climb switch on the dually though, but we really don’t have that many long steep climbs at the places I usually ride.