I want to have the most flawless and secure version I can possible have. I will be using paypal and credit cards for the payment system. I also have Moodle 2.0 and Joomla, and want to maintain the single log in feature. I presently have less than 50 members so the numbers are not much of a factor. I will be officially releasing my site in January and want to know what is best.
Currently there is no plugins for Joomla and Moodle, but these plugins will be available in next month for sure(and this meet your schedule I guess). Paypal is already supported by aMember v4. In regards to Credit Cards, we are working on Authorize CIM integration plugin right now and it will be available soon.