When I was a student, and when I spent a short while teaching electronic engineering at uni, this was my observation:
1) Give the students a bundle of notes as a hand-out (the pre-powerpoint equivalent) and they don't read them until 1-2 weeks before the exam, then they panic and come to you and its too late. FAIL.
2) Use the old-school option of making them take all notes in class and at least at one point they read them, and generally seemed to come to you with questions much earlier when there was still time to explain, revise, etc. PASS
Powerpoint is worse, as the modern style is "3 or so bullet points with bugger all text". Yes, in class you can do the explanation and cover the implications, but almost no one takes notes so you get the same problems.
And by time you have written a neat set of class lectures along with all diagrams and explanations it is a LOT of work. My experience was 2-3 hours to hand-write an hour lecture for my own use, but to do it neatly (with CAD drawings etc) and in full detail to make sense to a student, about 5 times that. At which point you might as well turn it in to a book and sell it...