I have invested a small amount into FreeMarket because I think it can do well, but that doesn't make me an expert on it by any means. If you are interested, I would recommend you to post here:

https://nxtforum.org/freemarket/

What I do know is that it does not log your ip, runs right on top of the nxt blockchain so transactions are very quick, listing fees are super low and buying fees almost nonexistent (1 nxt apiece), and it is already released of course.

I haven't researched openbazaar much though, it may have these features as well.

In my opinion, FreeMarket's devs seem to be a friendly and intelligent group, and seem dedicated. I think there will be more cool features to come