We compare the behavior of voters under simultaneous and sequential voting rules when voting is costly and information is incomplete. In many political institutions, ranging from small committees to mass elections, voting is sequential, which allows some voters to know the choices of earlier voters. For a stylized model, we generate a variety of predictions about the relative efficiency and participation equity of these two systems, which we test using controlled laboratory experiments. Most of the qualitative predictions are supported by the data, but there are significant departures from the predicted equilibrium strategies, in both the sequential and the simultaneous voting games. We find a tradeoff between information aggregation, efficiency, and equity in sequential voting: a sequential voting rule aggregates information better than simultaneous voting and is more efficient in some information environments, but sequential voting is inequitable because early voters bear more participation costs.