DNS optimization: Vanity dns
From the viewpoint of optimizing is it recommended to use "vanity dns" or not?
It's not entirely clear what you mean by "optimizing" in this case. In general though, the main reason why someone would want "vanity nameservers" is if they were acting as a reseller and they didn't want their customers to see the name of another company in the domain name of their DNS settings. If that's something that you don't particularly care about, then I wouldn't go through the trouble of setting them up. It's just another piece of infrastructure you'll need to maintain and another point of possible failure for not much gain.