Changed my frame in February and went through a real dilema over this. Decide to go for the full-suss.
A mate of mine was getting mega back pain after riding his HT. Swapped to a full-suss and stopped straight away, so no-brainer for him.
As for me, I only have one bike and it’s a 4″FS, Which serves me really well for the riding I do (Exmoor, Quantocks, SW stuff). I remember when I switched over from my hardtail and it was a revelation how much more enjoyable the bouncer was to ride. Blasting into a tricky root section just made me laugh out loud. I find 100mm is plenty for a bit of extra control and comfort without de-sensitising the trail. My mate had a 150mm and dropped down in travel as he reckoned it made everything a bit boring but didn’t feel he actually went any faster.
But, I’d really like a HT for racing, riding local trails (which are pretty smooth) and for winter, ‘cos they’re so much easier to clean when it’s filthy. I also really like the idea of all that trail feedback. I just wouldn’t want one as my only bike. If I lived somewhere like the South-East, I reckon a hardtail would be spot-on though.