My thoughts are unless OEM, most pattern radiators are built down to a price, not up to a standard.
So the difference between buying from a good parts supplier and not is the chance of a warranty claim within 12 months being accepted.
Don't get me wrong these days most people buy on price.
So all you can do is thoroughly inspect for any damage before fitting and return with photos for a claim if noticed, as many get damaged in transit.
If appears OK, fit it correctly, with correct corrosion protection antifreeze, pressure test for leaks if possible, give it a good road test and re inspect, then keep an eye on it for a few weeks if possible. Generally it will be OK.
Over a length of time cheap ones may corrode the aluminum quicker and other parts may deteriorate more than genuine, but by then any chance of a successful claim will have vanished anyway.

In the old days we and most garages could solder and repair faulty copper and brass radiators or a local company could re core them.
However plastic and aluminum modern radiators are "throw away" items when fail.
