@null does not really benefit anyone

I don't really have an opinion on whether paying to steem.dao or null is better but I would strongly disagree that paying @null doesn't benefit anyone. It benefits all STEEM holders by reducing the supply and reducing future selling pressure. Whatever is paid out, including to the dao, has the potential to eventually be sold on markets as selling pressure. Whatever is instead sent to @null will never reach markets.

It is certainly possible that funds sent to the dao will eventually be spent in a way that increases the value of Steem even more than what it costs in inflation, but it is also possible that is not true, so this is somewhat of a more opinionated and risky approach. Sending to @null is neutral and guaranteed to at least never contribute to reducing the value by selling or dilution.