Yes, download speed significantly impacts the PlayStation 3 online experience, though not always in the way players expect.
For a smooth experience, aim for at least 5 Mbps download / 1 Mbps upload. For competitive play or households with multiple devices, 15–25+ Mbps is ideal.
While raw download speed doesn't fix high ping, sufficient bandwidth ensures the "plumbing" of your connection doesn't burst when the game needs to pull data.