Hey there,

1) are there any known issues with using Membership Pro with EasyBlog?

To be honestly, I never use this Joomdonation Membership Pro extension before
Perhaps you can consult from their forums -> http://joomdonation.com/forum/membership-pro.html

2) what advantages come with using PayPlans?

what I know is Payplans can restrict any category how much post can publish it. And restrict how many post users can post. It would be best if you can consult with Payplans developer regarding this http://www.readybytes.net/

Hope this will help.