One benefit is evolution. If it turns out that one of the specialized cells is better than the other, than over time it will replace the less effective one. If all cells were the same, organisms wouldn't be able to adapt to different environments and evolve.
Another benefit is that with specialized cells, your body is able to become more complex. This complexity can lead to cellular ecosystems in which cells are able to form symbiotic relationships with other cells. For example is us, humans. We are a symbiotic relationship between many different types of cells.
Our lungs are able to aid our muscles which in turn aid our strength. Our heart pumps blood that delivers oxygen to other organs and muscles. And Etc.
Hope this helped!! :D
