We prove Feigin-Frenkel type dualities between subregular Walgebras of type A, B and principal W-superalgebras of type sl(1|n), osp(2|2n). The type A case proves a conjecture of Feigin and Semikhatov.Let (g 1 , g 2 ) = (sl n+1 , sl(1|n + 1)) or (so 2n+1 , osp(2|2n)) and let r be the lacity of g 1 . Let k be a complex number and ℓ defined by r(ki the dual Coxeter numbers of the g i . Our first main result is that the Heisenberg cosets C k (g 1 ) and C ℓ (g 2 ) of these W-algebras at these dual levels are isomorphic, i.e. C k (g 1 ) ≃ C ℓ (g 2 ) for generic k. We determine the generic levels and furthermore establish analogous results for the cosets of the simple quotients of the W-algebras.Our second result is a novel Kazama-Suzuki type coset construction: We show that a diagonal Heisenberg coset of the subregular W-algebra at level k times the lattice vertex superalgebra V Z is the principal W-superalgebra at the dual level ℓ. Conversely a diagonal Heisenberg coset of the principal W-superalgebra at level ℓ times the lattice vertex superalgebra V √ −1Z is the subregular W-algebra at the dual level k. Again this is proven for the universal W-algebras as well as for the simple quotients.We show that a consequence of the Kazama-Suzuki type construction is that the simple principal W-superalgebra and its Heisenberg coset at level ℓ are rational and/or C 2 -cofinite if the same is true for the simple subregular W-algebra at dual level ℓ. This gives many new C 2 -cofiniteness and rationality results.