Not to be the one to say this but a meter tells you exactly the same thing......
Absolutely...A meter tells you the same thing. A PP3 is also a meter where the PP1 and PP2 were not.
Do you work as a professional tech? If you do, and perform a lot of electrical as I do, I think you would find it a very convenient tool to have that allows you to diagnose electrical issues faster than a meter.
I have a Fluke meter that gets very little use in most automotive electrical issues I encounter. The meter is about the size of a brick but never seems to stay where you put it. So if you connect your test leads, it can be difficult to see the meter reading while balancing the meter on the air cleaner, fender well or radiator core support. Then the display can be difficult to see once you have your leads set. Now try viewing a meter when you are under a dash or inside a trunk, or inside a glove box, or a door panel.
The PP3 is much easier and that is why it is my goto tool for all electrical issues. After my initial assessment I may reach for my meter or even my scope, but first I goto my PP3.
Another thing about the power probe 3 is it kind of depends where most of your issues arise. I live in Virginia where rust and corrosion is not a big issue. As a result, most everything I experience is a component failure. I very rarely see a wiring issue. The PP3 lets me give power and grounds to verify the component very quickly. If I lived in the rust belt, I would probably experience more wire related issues than component failure. In which case I would use my Load Pro test leads by Dan Sullivan.
As I understand it, the new PP4 will be able to check resistance, and also the wiring all the way back to the battery. So I cant say for certain since I havent tried it yet, but it may eliminate the need for my Load Pro test leads.
Very rarely do I want outside power to a component, in vehicle hooked up to the harness tells me all I need to know usually with a backprobe, breakout harness, etc... 