A Subscription is the best choice if you or your client intend to continue using Jomres as a part of your ongoing business activities. The license is paid for monthly and it includes unlimited plugin downloads. The license does not expire until the subscription is cancelled so you have peace of mind that we are here for you and that you have unlimited downloads for an unlimited number of sites. Many of our users are using Jomres consistently and we've found that a subscription is the right option for most of them.
The one-off license ( Essentials ) is a good choice if you're a designer setting up a site for a client and you don't expect to change the site once it's up and running. Once the license has expired you will no longer be able to download updated plugins or get access to support, however you are not forced to uninstall the plugins, you can continue to use them indefinitely.
A more complete explanation can be found here.