Just my tuppence. I have a 661 pressure suit.
Yes it protects your from knocks and bumps, and would probably do a lot of good in the event of landing back first on a rock.
But it offers no protection against broken bones in general, your arms, neck, pelvis, legs, ankles, wrists are all still sticking out of this nicely protected core.
So the downsides are it’s heavy, and hot, and chafes my nipples, and does very limited work to keep you out of hospital. And on top of that you feel a combination of invincible and distracted by it so you crash more, increasing the likelihood of breaking anything sticking out of it.
Speaking to other DH’ers (as opposed to trail riders dabbling with an uplift) they’re not popular for exactly this reason, most ‘serious’ DH’ers just seem to wear knee pads.
I’d consider one of the backpacks with built in spine protection. And I like the ‘soft’ armour (3DO, EVA etc), but I’d not bother with the hard armour again.