La proxima vez vs La Proxima

Sometimes, at the end of the lessons, it says Hasta la proxima!  Sometimes "vez" is added for Hasta la proxima vez.
What is the difference between using the vez and not using it?

Thank you,
Roe 
 

No difference - the "vez" is implied if it's omitted. Going by what I've heard to date, it's more unusual to include it. In English, it would be like saying "See you!" with the implied "later".      (Now that I think of it, it would be more frequent for us to say, "Later!")

More unusual (to my ears, at least) is when people say, "Buenas!" (with the implied "Tardes").
 

Sí, estos lugares cuando el español de la aula encontrarse con el español de la calle puede ser muy confuso. 

¡Más tardes, güey!