Yeah I think Dylan Brown is the best overall defender who plays in the halves in the NRL going by long term track record, but Ethan Strange is mounting a strong challenge to that branding.
Dearden is the best cover defender but not as good in front up defence. Cleary is the best in contact and all that but he has these weird defensive howlers in him for whatever reason. Luai's also pretty good all around, he's just not as good of an athlete. Katoa good.
Worst defender in the halves is way more of a crowded field. DCE is underratedly horrible on that end.