Both do the same thing. The lowering brackets from UP are a set lowering setting and lowering links are adjustable.
Both have their arguments and r&d on why it’s better. I’m sure you can find UPs post on why brackets are better than links.
It’s a moot point saying why pay 5x the price etc.
LV, Chanel bags, etc do the same function as a $5 wallet from the dollar tree.
Good luck OP