gearhead is better than thick skin IMO
But it depends on the class and pred you are facing.
Against those preds who like to do the elder/stalker meta to oneshot using the disc or plasma, thick skin is more viable with most classes so you don’t get one shot.
I still prefer to use thick skin combined with OWLF for those cases, and for the rest just go with Gearhead for that extra syrette, ammobag or grenade
And never waste a gear slot on the self revival, ever. Is way too situational. Until they reduce the animation time, for me, is unusable. Most preds will claim you or shoot yoy before you have a chance to use it. And if your teammates are near, then there’s no need for you to use it. Specially with a field medic on the team