Hardtail I reckon. I’ve done the switch from HT to FS a few times but always end up back on a HT, I’m just finishing building up a Cotic Bfe to replace a full suss.
A full sus will be more comfortable to a point and may reduce fatigue but I have to agree with a mate who points out that a full sus can end up encouraging you to sit down more often which just puts more stress on your back anyway, a hardtail forces you to stand up a bit more which I find makes the ride more involving and fun anyway.
Having had a few full sussers I find them less responsive to rider input and on twisty, techy, rooty trails they can be harder to pump and pop off stuff (if that’s your thing). I’m sure people will be along to say this is just about adjusting your riding style to suit the suspension and pre-loading the shock etc but I don’t really want to change the way I ride to suit a bike.
I have a Specialized Pitch built up big and burly for local downhill riding but I reckon that until my back (currently 2 prolapsed discs) gives up once and for all I’ll stick to a HT.
Having said that it seems that a Thudbuster suspension seatpost works well to remove the worst trail buzz whilst keeping the nimble handling of a hardtail.
IF I lived in the Alps I’d ditch all of this and have a good alround 5-6″ travel suspension bike.