  This work addresses the comparison between active and passive RISs in
wireless networks, with reference to the system energy efficiency (EE). To
provably convergent and computationally-friendly EE maximization algorithms are
developed, which optimize the reflection coefficients of the RIS, the transmit
powers, and the linear receive filters. Numerical results show the performance
of the proposed methods and discuss the operating points in which active or
passive RISs should be preferred from an energy-efficient perspective.
