Comparing my Swift (71-72 HA) and a 456 Evo carbon 65 HA i think (currently rigid with Lurcher carbon fork 480 AC running it 650b).
I’d drop the Swifts HA a few degrees for a bit more stability on high speed downs. Though the ‘feedback’ is kind a fun and the immediacy has its attractions.
While the slack 456 bike certainly is more stable going down, and it doesn’t matter much going up, they’re a bit lifeless steering ‘going along’. You get used to it inside an hour, but the sharper head angles are better for steering around puddles and the like for us XC mincers: I think a slightly more responsive steer, is a bit more pleasurable on a few hours of undemanding just undulating XC, wheels on the ground.
I think for XC a high sixities is about optimum balance, for having a bit less sketch on a high speed descent and still some life in it when going along on an XC all day ride. HA is going to be as individual as picking wheelsize and gearing. Downhilling and bike park I’d definately say go slack. Actual singletrack, morw old school, especially rigid where you want to steer around things a bit more, I think its OK a bit sharper.