hey kray,
for both extensions when using the unlimited version you get installation service and support for unlimited sites where the professional versions only cover 1 site. also at easyblog unlimited you have some additional themes that aren't included in the pro version.

hope that helps

also here are the comparison tables:
http://stackideas.com/easyblog/plans
http://stackideas.com/easydiscuss/plans

Thanks for sharing Alex

For professional version do the other sites get receive updates or just the one?

Hey Michael,

I am sorry for the delay of this reply,

Do you mean update notification?

If yes, all the site also will get the update notification.

Hope this help.