Personally i think there are pros and cons, if that's the right description, to both full-suss and rigid/hardtail.
I have rode dh tracks on hardtails, on some tracks i am faster on hardtails, though to be fair i am a bit older now, so though i should still be able to get down them i would no doubt be a bit more steady. Which brings the point, already raised, that a full-suss smooths out rougher sections, and also raised is the subject of technique. Some bikes react well to riding through stuff, my original Giant Glory was so heavy that with decent suspension it just ploughed through rocks n roots, where as my Iron Horse Sunday which i had at the same time, was a lot lighter so you had to go light over rocks n roots, a technique i learnt on hardtails.
A lot of the trails i ride at the moment, Sherwood Forest and Peak District, i ride on rigid, im not out to set PB's or to see how fast i can go, but the bike is a lot easier to pick up and hop obstacles and gaps due to being a lot lighter. Of course following full-suss bikes i get left sometimes over the constant rough terrain and i have to stand, but that's how i have always rode. A long distance ride through the mountains would be nicer on a full-suss, to keep at bay the beating of days worth of smashing into things, but im sure i would notice the weight more going up hills or lifting the front wheel over obstacles
At the end of the day though, they are both bikes, can do pretty much the same things, i have only rigid ride-able bikes at the moment, it doesn't stop me going out and riding trails or in the hills.