I just received my new Porsche piwis iii tester and I would share my thoughts since I have used Durametric cable clone, PIWIS II and the 3 now.
The review is based on CnAutotool.com PIWIS 3 (#VX16-B)

OEM Porsche PIWIS 3 Tester III Diagnostic Tool V38.900.000 PT3G with 128G SSD with Panasonic CF-MX3 Laptop
Why I bought the piwis iii?
Durametric cannot do the coding I need. it has very very limited coding abilities, a PIWIS can could absolutely anything.
Since the PIWIS 2 is obsolete I don’t know if Porsche is supplying updates for it. The only issue I see is that the newest variants of certain modules will not be able to be programmed.  All of the 2’s I see have the last software that was issued a few years back so there may not be updates for it. If you buy used modules with the same version as the one you remove then this isn’t an issue. Since module replacement is an unusual thing unless you buy a flood car like me I don’t see this as an issue.
The piwis 3 is faster but the tablet one might be equally fast. My particular 2 never worked well for guided fault finding and my three is better but refers to documents that only dealers have.  It supports all the older models that PIWIS 2 supported as well. PIWIS 2 is limited to <2017.  2018 versions and newer have no choice but to buy a III version.
How does the piwis tester iii works?
I should be more precise as I did not purchase an actual Piwis III. It is actual a factory tool and currently sells for $5,900 which was way too rich for my blood. It is in the factory carrying case with all the cables and WLAN cap for the VCI that plugs into the usb mini port and allows for wireless connection to the car, along with the multimeter and oscilloscope cable.  What I bought, which sells for around $2,000 and what is for sale in most places, is a Lenovo laptop with Windows 8.1 installed and the Porsche PIWIS III software (Current version is 38.9) installed and includes a USB wired VCI the same one the factory tester uses.  I both cases the VCI and software have been modified to disable factory authentication and naturally there is no automatic updates. If you did have a PPN account, this tool would update normally. Most offer one year of updates and then charge for subsequent years. It should be known that the updates are really for adding new model years, not software changes. On to the review.

It is a nice laptop with a touch screen and a screen pen included. The Porsche software starts automatically, but the Microsoft button functions and you can do other things at the same time such as TeamViewer or open an internet page. The VCI ( the part that connects to the diagnostic port) is smaller and the cable connecting is shorter, but it is a standard USB to miniUSB cable so you can purchase an longer one anywhere.

The tester can be changed from after sales mode to developer mode which allows for a lot of special features ( looking at you who want to disable start stop permanently). The software is faster, and easier to use than the previous version. For example on the diagnostic program, the tester auto detects the car model. Just plug it in, turn the key on and it does its thing. For me, I’m not sure if it is a function of the unit I have or not but the guided fault finding works well. Click on any fault and press the fault finding button and the unit tries to provide you a diagnostic plan. The plan is better and the English description is better. I haven’t tried the wiring diagram software but I imagine it works as well as the previous version.

There is a new ODBC program on the unit that reads standard ODBC codes, I am wondering if this unit can be used for other cars for simple code reading. I will try it on a buddy’s car next week and let you know. There is a oscilloscope function and a multimeter function but the laptop clones don’t come with these cables.

The PT3G interface runs on my 996 Turbo and I’ve used it to PPI 2018 Panamera Cayenne and a 2019 911 with no problems.

All in all it is a better tool but really can’t do more than the 2 can do, only faster and on cars from model year 2018 to current which the 2 can’t do.