You are wrong that a speed improvement is the only reason to use our over use vars. (In fact I am not absolutely positive that it is always a win.)

The difference with our is that the declaration is lexical, not global. So using our in 3 functions becomes an alternative to a global that is globally accessible, or a private block with a lexical variable.

Personally I don't consider the win over use vars to be compelling. In fact if you are going to be sharing a variable in several places, I don't like having to synchronize the declarations. Hence for most purposes I actively prefer use vars.

However that is an opinion decidedly at odds with many other people. Hence the above may prove useful if (unlike me) you are in a predominantly 5.6 environment and like our.