Meteor - Why should I use this.userId over Meteor.userId() whenever possible?

Question

Judging from this comment by David Glasser in the GitHub issues:

this.userId is the primary API and Meteor.userId() is synta

Answer 1

Simply speaking, Meteor.userId() queries the DB everytime you use it. In client side ( logically ), it looks fine - since we have minimongo.

In server side, using Meteor.userId(), consumes extra resources on SERVER, which, at times is undesired.

Now, this.userId is more over like a session variable m ie it will have a value only when there is a userid attached with the current session. And hence,using 'this' reference wont go and fetch the database everytime, but rather than that it used the active session userId.

Consider performance as a factor. That is the main reason for using this.userId rather than Meteor.userId