Members-only password protected areas can sound like a good idea. You can sell access to ‘premium’* content, for example. They’re certainly doable on our sites. The problem is that you’ve got a choice: put a password on material which is the same for everyone (and so if it gets posted somewhere else, everyone can access it) or give / sell people accounts on your site.
The latter can be limited in what they can do (such as only see stuff that non-members cannot) but WordPress has an unfortunate history of allowing such accounts to gain, through various dubious means, total control over the site. Currently, there are no known ways to do that, but there’s been at least one or so a year in the nine years since the WordPress project started and I would not want to bet that there will not be another one.
So if you’ve got content to sell, I suggest** that you hold your nose and use AW. In any case, my recommendation*** is that you do not go down the ‘accounts on your site’ route.
* Marketing speak for ‘expensive’ :)
** Consultant speak for ‘have a very good reason for not doing it this way’ :)
*** Consultant speak for ‘do it this way or else’ :)