The standard focusing screens make precise manual focus very difficult if not impossible. You simply can't *see* well enough. A properly calibrated AF system will win against standard screen MF.


With practice, a split prism screen or super-precision matte can achieve more precise MF but I don't feel like it would be faster than AF in many situations.


As for MF in Live View, provided you can hold the camera still and the subject isn't moving, you can almost always nail focus. I like using this method for stationary subjects while on tripod. Handheld is more difficult because you're introducing a lot more camera shake by holding the body away from your face.