  We use localization techniques to study several duality proposals for
supersymmetric gauge theories in three dimensions reminiscent of Seiberg
duality. We compare the partition functions of dual theories deformed by real
mass terms and FI parameters. We find that Seiberg-like duality for N=3
Chern-Simons gauge theories proposed by Giveon and Kutasov holds on the level
of partition functions and is closely related to level-rank duality in pure
Chern-Simons theory. We also clarify the relationship between the
Giveon-Kutasov duality and a duality in theories of fractional M2 branes and
propose a generalization of the latter. Our analysis also confirms previously
known results concerning decoupled free sectors in N=4 gauge theories realized
by monopole operators.
