I have found in life that there are a few times you can afford to be cheap & I understand people have budgets so let me break this down a little. So you save $300-$400 initially
Like the DR. said, they have actually inspected & "found lots of quality control issues" Knowing Chinese business practices pretty well (inside track stuff) I would not want to hope they fixed those issues. If this diff decides to let go, what else is going with it? Let me help Ring & Pinon $$$, new carrier & pinion bearings, seals. did it decide to frag & penetrate the diff cover/ Add more $$$. Did it do what it really shouldn't as a limited slip & total lock up take an axle stub or 2 with it? $$$ Oh & do you need to pay someone to install it all? $$$. This adds up to far more than the $300-$400 saved each $ is a actual place holder on what it will cost. What about the tow bill & your down time $$-$$$
I have seen plenty of diffs grenade & installed plenty of gear sets to know that this is not an area I would buy an inferior product. Most people who install a performance diff have a plan to push the car. Will you take the gamble on how long this will last for you?
personally I would wait until the other option became into your budget or saved for it. Do it right, not again!
Good luck