Hi All,
I'm a little late to the discussion, but I thought I would share my findings.
The information I can share is as follows:
1. I have used a local sql database. Easy to setup and easy to use if you are used to writing sql statements. The drawback is that you will have to write your own sync methods / api calls, and it's a pain the backend to update if you need to.
2. Couchbase (not to be confused with couchdb) -> pouchdb (local on the phone) with integrated facebook authentication via a couchbase sync gateway. This is great, it deals with all of my requirements being that I have a local database (noSQL) so my app is off line, I have a cloud store which each app can sync with (mobile, web, etc). The draw back is that it's not a cheap option. The downside is that it took a fair amount of time to setup and there are quite a few gotchas along the route.
3. Parse.io - This looks great - I have only had a dabble with it but the docs look good and the implementation looks straight forward (and the pricing is great for initial development). I haven't yet found parses' pouchdb counterpart, if I can then I would probably take this route for future development.