render partial vs. render subtemplate?

Can anyone shed any light on the pros/cons of one vs. the other?
Certainly the "render partial" option is advantageous as an
abstraction of one or many objects and what to do with them. But I'm
noticing that my code is starting to have lots of partials and I
wonder where subtemplates fit in?

Are there some best practicies for partials vs. subtemplates?

Thanks!

-Danimal