Parker is more proven but since his loss to Whyte 2 years ago he hasn't done much fought 3 times against Flores, Leapai and Winters. In the same time frame Joyce has won the commonwealth title vs Thomas, beaten Bacurin, Kiladze, Hanks, Stiverne, Ustinov, Jennings, Wallisch and Dubois. If we go based on what both fighters have done lately then Joyce is the more deserving. Parker has had his title shots, his unification fights, his shot at other top contenders but recently he's just been treading water and sitting on his ranking. At least Joyce has done something recently to deserve a potential vacant title shot. Parker would be the likely mandatory afterwards anyway as he's 3rd in the rankings.
He's not going to slaughter anyone, he's with the proper big boys now. People talk like he's some kind of killer in there. Here's a newsflash for you, he isn't.
Dereck is good, he just is very slow and predictable boxer. Sadly now here are not around Klitschkos and Povetkin is not 30-34 years old. After these guys in their prime he rushed back to CW to fight with the same Dorticos, Briedis ( Usyk's fans claims how impressive his win was and dumbasses prize this nonsense, Usyk was lucky that he wasn't boxed like Glowacki boxed vs Vlasov ). and Dorticos ( most likely he now will switch Usyk's lights off in distance ). Tabiti to test him further.