As far as I know, it's just a self heating metal rod with grounding. If the heater, tip design & plating and PID formula is same, they'll perform equal.
There is no PID. There is firmware only for the interface and display and for user calibration, which are easy to duplicate. There is nothing special about the electronics, at all. If you can wire a comparator to a triac and do temp sensing with a thermistor amplified and buffered by opamps, you have as good a circuit as a 936 or an 888. But the performance doesn't much come from the electronic control circuit.
Other than supporting Hakko, the main reason to buy a real one are
1. Materials. You can think plastic is plastic, but it's not. The plastic at the front of the handpiece is exposed to high temps, and many clone handpieces will eventually break in half after 2-4 years. The really sketchy ones will actually melt if used at high temps.
2. Construction and tolerance of the heater. There are many clone heaters that vary in quality, and I think all of them are constructed of wound nichrome wire element with a ceramic cover. These are usually a looser fit. And they have a limited life expectancy. Probably 2-4 years, and they will burn out.
I have heard the current Hakko element uses a film element. W/e the case may be, it performs better and it lasts longer. You can buy replacements, but AFAIK, the only reason you would need to do that is if you drop and break it. It is also probably more resistant to breaking than some of the clones.
3. Power supply. The 888D meets spec under load. Clones may or may not.
So even with equally good electronics (you'd have to a total idiot to not be able to replicate the electronics), I've used many clones that are obviously inferior in power and/or thermal coupling, as well as efficiency (regarding how much of the heat gets to the tip vs burning up your hand). If the clone meets your needs, and if 2-4 years is longer than you really care to plan ahead for, then a clone might be a good value. In 2 years, you could be using $600.00 stations or you could have thrown away all your soldering equipment, because you don't care to do it, anymore.
This particular clone might be better than most, but I wouldn't know.
I'm not a tool snob. I have expensive tools and cheap tools, and sometimes you can't tell the difference. Sometimes you can, but the price difference makes the cheap tool a good value. Sometimes the real thing is the bargain. I can't say where the line gets drawn for anyone else, but the genuine Hakko 888/888d is pretty damn good. Don't let the high cost of replacing a handpiece concern you. It is built to last. I hope I outlive mine. I wouldn't bet on it.