There are pluses to both.
Adopt and you give a discarded rabbit a home but, it may or may not be trained at all, might have vices you don't want. Will be older so, won't be with you as long. Will 99% chance already be spayed or neutered. (that can be good or bad depending on your views.)
Buy from a breeder: Probably less costly, you get a young rabbit, you give a rabbit that might have been used for fur or meat an home as a pet, you get to see where the rabbit was born and the parents, and insure all rabbits there appear healthy and, you get to train the little one your way, it doesn't have bad habits because it has never had a home. It may be more shy of you at first, but it will come around if you are patient with it. It won't be spayed or neutered, so it would be your choice to do that to it or not.
It's up to you. You can get a wonderful rabbit either way.