I've been looking at VOAs and UOAs of 5W20 and 5W30 for GTX, Magnatec and Edge, both from BITOG and PQIA.
It seems the modern GTX, both regular and UltraClean has an add pack that looks something like this:
Moly 80 ppm
Boron 200 ppm
Zinc 800 ppm
Calcium 2300 ppm
The Edge has a bit more variation, but it's much the same as above, except with 7ppm Titanium, and a greater variation in Boron 100 to 400 ppm. But all up has a similar inorganic add pack from looking at the simple UOA & VOA analysis.
Now Magnatec semi-synthetic and the few full synthetics I've seen look something like this :
Moly 15 ppm
Boron 20 ppm
Zinc 700 ppm
Calcium 2200 ppm
The Mo and B is definitely lower, but I would not be surprised if the Zn and Ca match the Edge / GTX levels, but I have no VOA to estimate depletion, only UOA numbers.
(Also, the lone Australian Magnatec 5W30 SS better matches the GTX / Edge add pack. )
As for oil bases, traditionally GTX is a mineral Group II, Magnatec is a semi-synthetic and Edge is a full synthetic. But things are moving forward, with GTX UltraClean now being semi-synthetics, most Magnatecs being full synthetic now, and the Edges are still full synthetic plus the only ones known to contain PAO.
So in terms of organic base oil: Edge >= Magnatec >= GTX
In terms of inorganic add pack: Edge > GTX > Magnatec
So to me it looks like GTX has a great add pack which has been improved a touch more (extra Ti & B) for the Edge, while the Magnatec has a fairly standard add pack (low on Mo and B).
This sort of makes sense to me from a development / economic point of view, as it implies a matrix of development. Give GTX the good add pack, give Magnatec the good base stock, give Edge everything and a booster shot of Ti and Boron.
Caution: this is all me guessing, I have no real insider knowledge.