Hydroboost all the way!!!!!
The only time I've noticed any steering assist change (my Excursion, and all the 99+ SuperDuty Diesel Trucks have Hydroboost factory) is when I am at idle, and trying to maneuver and have my foot on the brakes. Best example I can give is: I work in an area where I have to park in a parking garage. The quarters are tight in there, so you have to move more slowly, and have to ride the brakes. In this situation, the assist on the steering is much less, but the braking works fine (I think the brakes have priority). So I have learned when to lift off the brake just long enough to steer. Didn't take very long to learn this new trick, and the better braking is worth this little quirk. I've not had any issue at anything above idle and steering....