It seems like finding a board in stock somewhere is challenging/ SuperBiiz has the ASROCk Rack EP2C602-4L but I have no experience with them. I would prefer an ASUS board if possible but they are far and few between.
I'm not sure that I understand what you mean. I guess you wanna know why I went with the more expensive one?
Well, it is a sort of standard form factor. So it will fit in my case and most screw holes should line up. I guess that is a feature. Other than that, more USB, 7 (seven!) full size PCIe slots, SLI / CF support, more SATA instead of SAS and the amount of cables and stuff it comes with. I don't know how stripped down the UEFI would be in the Z9PA and I have no idea if XMP profiles are supported by the server board. Than there is other stuff that is less important for me right now like onboard sound and so on.
In the end you have to decide if those features are worth the money for you but I think 150,- bucks for all of that, yeah it is for me.
It's missing USB 3.0. And it does not have a SAS controller.
For USB 3.0 you'd have to buy a controller card, which is still cheaper than the WS board. You can also buy a SATA PCIe card. That reduces your available PCIe slots to 1 and the PCI slot (if you take a Dual Slot GPU). The question is: What else (apart from a soundcard maybe) do you want to put into your machine?
Out of the fact that you complain about 150€ and about shipping being expensive I derive that you are somewhat of a Pfennigfuchser (cheapskate sounds a bit harsh). So I think that the 7 full size PCIe slots are not really useful to him because he will probably not just drop 3 additional GPUs in his system. Same goes for the 4 missing SATA ports: I find it unlikely he will have too many hard drives.
You will be waiting a long time for a deal on the z9pe-d8 ws. It carries an annoying premium. The guys over at 2cpu seem to have plenty of expertise with the board.
Figuring out ES chips for v3 / v4 seems to be being discussed on serve the home right now. I'm probably good for this year with v1/ v2 or at least till the shopping list for everything else thins out.