What's the easiest method for migrating content from Drupal 7 to another Drupal 7?
You should use the Features module to export the configuration for your content types (and any related things - taxonomies and the like).

To move content between the sites, I'd recommend looking into the Deploy module, which will allow you to "push" content from one site to another. It requires some configuration to get it all set up, but it works really well, particularly with nodes that have dependencies on other entities (via entity reference or taxonomy term reference or things like that).

If you want to use Migrate (which is probably not a bad idea, depending on your data). You could also look into the migrate_d2d module, which has a UI that let's you just point at another Drupal site, and then press "Go" and it'll pull in all your content.

tl;dr: There's lot of ways to do it, but the "best" way depends on the data in your sites.