Sadly, no difference. Another site I have that has AcyMailing 5.10.4 installed has found a new version (5.10.13) if I use the "Check Update" within the component. The Joomla Extension Update finds no update.
The site that is on 5.8.0 finds no update in either place.
EDIT: If I try to update from 5.10.4 to 5.10.13 I get taken to the AcyMailing Subscriptions page and it tells me I have no active subscriptions, and I cannot update from 5.10.4 -> 5.10.13 :-( I am only using the Starter product.