Most of the manufacturing defect concerns that I have are with the smaller diameter quicklinks. Smaller rod size and rope wear makes a 1/4" unrated link a time bomb IMO. I like beefy anchors and install beefy anchors that will still be around long after I am gone.
Once you get into 3/8" diameter links then the safety margin increases to the point where they are pretty reliable. Beyond that it is really a question of preference.
I buy most of my gear at cost so the comparative price points are very reasonable. I buy a box and use them up and go get another one.
Interesting, because I remember the day when many fixed rappel anchors on this side of the Pond were straight from the hardware store. To me the best news was that even old "climbing" 'biners were much stronger than new "hardware store" ones.
As for 1/4" anythings, if nothing else, the relatively sharper edge would greatly diminish the breaking strength of anything passing over it.
When I broke the rope with the 1/4incher i made certain that the rope bearing surface was a standard carabiner. the rope did not and never has broken over the edge of the connecting biners or quick links. It always breaks at the knot.