Again : Pro Sites vs Memberships 2


I understand Pro Sites enable to sell subsites in multisites with different levels, I have a network installed with Pro Sites already

I understand Memberships 2 enable to sell/protect access to CONTENT, I have Memberships 2 installed already on a single WP install to protect content access

However, they both offer subscription, with recurring payment - I tried many things + read articles before asking, but some are outdated : how Pro Sites and Memberships 2 work together still isnt clear

Do I need Memberships 2 in 2016 in order to sell my subsites on my Pro Sites network ?
If it's optionnal, what will I have more using Membership+Pro Sites compared to using Pro Sites alone ?

Thank you !