This paper presents a comparative study of three operation modes for an aerial manipulation robot, considering as illustrative application example the realization of maintenance operations on power lines while flying, holding, or perching. Relying in our previous works, and taking into account practical considerations and limitations of the aerial platforms and the manipulators in outdoor scenarios, this paper provides a qualitative and quantitative evaluation and comparison of these three operation modes, identifying some relevant factors that determine the reliability of the system in the realization of the intended task. The paper is mainly focused on lightweight and compliant dual arm manipulators that allow the realization of dexterous and bimanual manipulation tasks on flight, as well as the use of one of the arms for estimating the aerial robot position with respect to a grasping point, or exploiting the kinematic redundancy of the arms to maintain the equilibrium while perching on the power line once deployed in the workspace. The paper also considers the dynamics and control of the aerial manipulator in the usual decoupled scheme, identifying the key terms in the model that determine the behavior of the coupled dynamics according to the particular configuration of the arms when integrated in the aerial platform.