The normal power feed only replaces the hand wheel temporarily while using the power feed. Then you plug back in the hand wheel and use it manually again.
The lead screw power feed system gives you instant access to your power feed without having to remove your hand wheel and uses a heavier duty gear motor so it is made for running a lot more taper passes.
The advantages of the lead screw power feed are mainly ease of use. It is there ready to go anytime you turn it on. It also is designed to run for hours on end. The hand wheel replacement type of power feed is more for limited use, but in my opinion does just as good of a job. The advantage of the old style hand wheel replacement type is when not in use you have a much finer hand wheel revolution. It moves your carriage about 2/3rd and inch with every rotation. Whereas the lead screw type gives about 1.8" carriage travel per hand wheel rotation.
So all things considered, if your work will be mostly repair work then package one with the old style power feed might be the way to go. But if cue building is going to be a large percentage of your work then the lead screw power feed is the way to go.