Both are great but the seedling is a ripper.
While I accept that anitum and adductum are the same species, I still prefer to label this hybrid as WBW.
Well, as the result of their hybridization with rothschildianum show up so clearly and stablely different (for one), I think, that you, if you prefer to see them as the same species, should at least grant them varietal status!
And someone should teach the AOC, that the registrar at RHS is the authority, when it comes to hybrids! Not Kew! They can agree or disagree as to whether adductum and anitum are separate species - but in so far as RHS has the cross between rothschildianum x anitum as Wössner Black Wings, they have to take the discussion with the registrar at RHS before they can change the name of the hybrid! Everything else is willfull behaviour!