That’s like comparing a Mercedes S Class to a Kia Forte. None of the aircraft in the PD edition are anywhere near the level of fidelity of PMDG. Hell, they’re not even up to the level of Carenado, which are basically eye candy, but with all systems working.
The real issue is the pricing structure. If someone’s already forked out the price for the Standard Edition, it costs almost as much as having bought the PD edition outright from the start to upgrade to it.
But that was likely done by design to maximize profits, knowing most people would “cheap out” and buy Standard out of the gate, then want the “exclusive” planes in PD later. I know I regret not just buying the full PD right out of the gate. I had to pay that high price of admission to get my steam gauge 172 and Baron.