Difference between DRUPAL_CACHE_PER_PAGE and DRUPAL_NO_CACHE What is the difference between DRUPAL_CACHE_PER_PAGE and DRUPAL_NO_CACHE? 

I'm developing a module that will generate 2 blocks for menu and it's sub-menu in different blocks and can't decide between those two options for the blocks. 

links:
https://api.drupal.org/api/drupal/includes%21common.inc/constant/DRUPAL_NO_CACHE/7
https://api.drupal.org/api/drupal/includes%21common.inc/constant/DRUPAL_CACHE_PER_PAGE/7
DRUPAL_NO_CACHE doesn't cache the item, ever.
DRUPAL_CACHE_PER_PAGE caches the item per page url -- this is useful for example if the block changes with a url context.