This study compared a picture exchange (PE) system and an iPad®-based speech generating device (SGD) when teaching requesting skills to preschoolers with developmental disabilities and limited functional speech. A multiple baseline design with counterbalancing the order of two instruction conditions across participants was applied to compare the acquisition rate, followed by a concurrent operant arrangement to examine participants' preference for these two augmentative and alternative communication (AAC) systems. Discrimination of two picture symbols presented via the priority AAC system was also probed using a concurrent operant arrangement. Results indicated that two of three participants required less sessions to reach mastery for the iPad®-based instruction condition. All participants showed a clear preference for the iPad®-based SGD and were able to discriminate between two picture symbols presented simultaneously on the iPad®-based SGD when making requests. This study highlights practice implications in terms of describing a systematic approach that could be employed when identifying a priority AAC system for learners with developmental disabilities and limited functional speech.