  We show that the recently proposed large $N$ equivalence between ABJM
theories with Chern-Simons terms of different rank and level,
U(N_1)_{k_1}\times U(N_1)_{-k_1} and U(N_2)_{k_2}\times U(N_2)_{-k_2}, but the
same value of N' =N_1 k_1=N_2 k_2, can be explained using planar equivalence in
the mirror duals. The combination of S-dualities and orbifold equivalence can
be applied to other cases as well, with very appealing results. As an example
we show that two different quiver theories with k nodes can be easily shown to
be Seiberg dual through the orbifold equivalence, but it requires order k^2
steps to give a proof when Seiberg duality is performed node by node.
