The wardens it will come down to cost and if they fix the damage on custodes weapons.
The main problem is that the codex units are kind of overpriced and their weapons have variable damage. Especially since most of them are foot slogging. Allarus have a lot of things going for them due to strategems, but the damage is still questionable. The best units are saggitrums because they have some pretty nice shooting and thus make good back objective holders. The venatari are better bikes because they are almost as fast, have devastating shooting, and have a shield that doubles as a power axe, and the galatus dreadnought because they're just crazy. Ofc all these units have 9th Ed rules because they're forge world.
The warden I think will never be too good due to load out. Unless they get some new crazy ability or strat