Wasn't that one reason the face blind handles were abandoned, one it gave fractional seconds of indecision between which to use and the other it bent you forward as you pulled it, where as a handle between your legs tends to make you you sit back in the seat when pulled.
AFAIK the face screen puts you in the better posture? i.e. more naturally rather than seat pan where it needs to be practised.
Main reason for seat pan initially was negative 'g'. Then with the Mk9 or so, dispensed with the top handle.
Interestingly, the Mk4 - in the JP and Hunter - with 2 handles, uses the bottom handle as "preferred" in the JP, but the top in the Hunter.
Hunter ACM, with seat pan, emphasises head position v spinal injury. But also says seat pan quicker / better under positive 'g' or if canopy has gone.
NoD