I have extremely limited experience with buffering substrates since I focus mainly on neos, however I did like Up sand when I was using it. Some people say it doesn't last too long with tap, buut since I was using RO I found it lasted a very long time for me. Even up until I broke down the tank.
Also Up sand doesn't leech ammonia. It did drop the ph to 6.3ish, which is a little low, but I didn't have to wait for months for it to cycle.