A lot of the more advanced holders made there are garbage. You get what you pay for. You're asking all the right questions but you're still getting drawn into the local "buy cheap" mentality.
The problem with milling chucks, hydraulics, etc is that they're unforgiving if a tolerance is blown in manufacturing. The holder needs to be trashed because it can't correctly grip a tool... in stark contrast to a tapered collet holder where a blown grinding job simply means bad runout. But what happens a lot over there is that they don't get trashed. The managers turn a blind eye and ship the bad product to the customer and shrug when shit hits the fan.
I've used a milling chuck made by one of the better companies there and a 1/2" aluminum endmill pulled out almost immediately.
See, now this is exactly the kind of thing that makes me paranoid. I read the other thread with the guy who gets tool holder fretting, and I'm thinking there is really no way to check that any of the tool holders will perform as expected until measured. Last time I bought a set of tool holders from this local company 2 years ago, they were all nearly perfect in measured runout and the external quality looked nice as well. But I didn't have the tools at the time to check torsional clamp strength and pullout resistance.
I also bought a set of cheap Chinese Alibaba tools to compare, imported them into Taiwan, spent like 300 dollars to see if they were viable. Nope. They claim 5 microns runout and measure at 30 microns for the SK16s. Horrible. Maybe OK for a flycutter?
I'll probably end up buying a set of BBT30s for the new machines, then I'll have to exhaustively check their taper contact, flange contact, runout without tool, runout with tool, runout at 4xD, torsional gripping strength and pullout strength. I'll make a detailed post on this forum when I have the results, which will hopefully be in a few weeks.
If the Taiwanese made tools have good runout but low grip force, that must mean the collet taper angle isn't perfect. I figure a good grind job would actually make the big end slightly too small, because it expands more than the small end when the collet is expanding it.
@Orange Vise You don't have to say their full brand name, but does the company you bought that milling chuck from start with An or Sy? BTW thanks for your feedback and advice so far in this thread!