Which language will get you deeper into Buddhism, Pali or Sanskrit?

I seem to have read that the "original" or "oldest" Tripitaka was written in Pali, but at the same time the Sanskrit language is much older than Pali. How do Sanskrit and Pali relate in terms of Buddhism? I would like to collect as many Buddhist terms and their meanings in one of these two languages but not sure which would provide the deepest, most concise, clear, and complete terminology for the Buddhist cosmology and theories of mind and such. Sanskrit seems like it has a richer more established etymological system so it might be easier to understand concepts that way, but perhaps Pali is closer to the original meaning or something? Which language would be better for a beginner or advanced student of Buddhism?