This study evaluated acquisition, preference, and generalization of two forms of augmentative and alternative communication (AAC) during functional communication training (FCT) with two students with autism spectrum disorder (ASD). Acquisition of FCT responses, using a picture-based communication system and speech-generating device (SGD; Apple iPod Touch with the Proloquo2Go), was compared. Following acquisition, preference of response mode was evaluated for each participant. Both AAC systems were made available simultaneously during FCT sessions, and data were collected on participants' initiation of functional communication (FC) on each modality. Findings indicated FC responses with the picture-based communication system and the SGD were acquired with similar rates by both participants. Furthermore, both participants demonstrated a consistent preference for the SGD as compared with the picture-based communication system. Both participants generalized the preferred FCT mode (i.e., SGD) to their classroom setting with their classroom teacher. Results indicate it is important to assess both acquisition efficiency and preference when selecting AAC systems for individuals with autism.