Reasonable scale means... what exactly?

Here's my opinion: just use postgres. If you're experienced enough to not when I say that, go for it, the advice isn't for you. If you aren't, I'm probably saving you from yourself. "Reasonable scale" to these people could mean dozens of inserts per second, which is why people talking vagueries around scale is madenning to me. If you aren't going to actually say what that means, you will lead people who don't know better down the wrong path.