  We compare quantum Otto engines based on two different cycle models: a
two-bath model, with a standard heat source and sink, and a measurement-based
protocol, where the role of heat source is played by a quantum measurement. We
furthermore study these cycles using two different `working substances': a
single qutrit (spin-1 particle) or a pair of qubits (spin-1/2 particles)
interacting via the XXZ Heisenberg interaction. Although both cycle models have
the same efficiency when applied on a single-qubit working substance, we find
that both can reach higher efficiencies using these more complex working
substances, by exploiting the existence of `idle' levels, i.e., levels that do
not shift while the spins are subjected to a variable magnetic field.
Furthermore, with an appropriate choice of measurement, the measurement-based
protocol becomes more efficient than the two-bath model.
