It has been postulated that of the "Fauxia" offered to buyers, there exist two versions of the circuit board; one early and one later.
Further to this, one Irish bloke who's got a bit of experience says the later one can be reflashed to run DiagBox while earlier design boards cannot. The virtue of newer versions is simply that you know you have access to the most up-to-date info on firmware for each module/component.
The other difference between some offerings, is that downloads (sundry ECU software updates) are not possible with some. You can see the file list but not install any. I cannot isolate a pattern, version or seller in this comment.
Finally - no diagnostic software is a subsitute for mechanical experience. You can on occasion, spend as much time rooting about with a handful of known codes, as if you just worked from first principles. The benefit here, is you can nicely clear the faults log once done.
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cript: I don't think $400 all in for a bunch of knowledge and "power" is bad value.