[krogsgard]

I don't know much about the ones you've listed, but I've talked to the guys that made Memberful, and I have a couple thoughts as to what might make theirs different:

1) Recurring payments. I don't see anything about recurring payments on the links you provided. I know Memberful will be offering subscription / recurring payment offerings.

2) Simple integration with WordPress. These guys are behind Theme Foundry, a WordPress theme shop. So a priority for them is to make it really easy to integrate Memberful with a WordPress site. Since WordPress has such a huge marketshare for self-hosted CMS based websites, that's a big plus. Site owners won't have to worry about PCI compliance, SSL, etc.