This paper investigates state estimation performance for sensor systems with synchronous sampling and asynchronous sampling. It is assumed that system dynamics are described by a class of scalar discrete-time linear systems and a Kalman filter is implemented. The sensors in a sensor system with synchronous sampling are synchronized by a synchronizing signal, and all the sensors work at the same time. Sampling rates of a sensor system with asynchronous samplign are determined stochastically and not constants. It is demonstrated that synchronous sampling is not always better than asynchronous sampling. In particular, this paper gives a sufficient condition, in terms of system parameters, for the estimation performance of systems with asynchronous sampling to be better than synchronous sampling.