I haven't really looked at 48 Bass Chinese instruments, though I have looked at and listened to quite a few 96 & 120 Bass accordions. I have also spoken to people I know and trust, and have visited numerous websites which feature Chinese instruments.
I have had good reports about Black Diamond Accordions, though my knowledge of them is limited. My personal choice of a 72 Bass Chanson has left me with no regrets. It is an instrument I use every day, and it works perfectly well.
The pros and cons of buying new Chinese or second hand European creates a dilemma, though I am quite happy to consider a new Pearl River. The Pearl River company is (I understand) the biggest piano manufacturer in the World, with Steinway & Son trusting them to build three of their piano models. In fact, Pearl River manufacture huge numbers of instruments for leading brands, so they must be getting something right.
In the early 60's, I owned a few motorbikes. These included Ariel and Norton which, at the time, seemed peerless. My friends & I laughed at people who bought Japanese bikes, thinking ourselves much smarter than anyone who rode a Suzuki or Honda. We all know what happened over the next few years, so I am reluctant to tar all Chinese instruments with the same brush for fear of looking stupid.
The laptop I am using to type this comment was made in China, as is the TV, DVD player, Set Top Box and pretty well every other electrical product we own. We had all better get used to the fact that the Chinese are capable of making good quality products at very reasonable prices, and that European manufacturers are right up to their necks in farming out manufacturing in order to maximise profits.
At no time have I ever criticised European Accordions, and I can only conclude that criticism of Chinese Accordions is just a rather lazy generalisation. Sure there are rubbish Chinese boxes out there ..... I know of a few that I wouldn't touch with a barge pole, but I also know that there are some very decently made ones available for those who take the trouble to look.