For tech savvy folks: is Dropbox the best alternative for collaborative file sharing?

Here’s what I’m looking for to recommend to someone.

1.) free
2.) easily accessible for all
3.) has an app for both IOS and Android

She is currently using box.com but its a bit unwieldy because everyone has to send her their email addy so she can send them a link and to add them as “collaborators”.

I’m assuming Dropbox is less awkward? Or is there something else better, easier?

These are currently PDF files and there is no privacy requirement at all. Anyone on the Internet can view them.

More specific details are at this link. If you have any other Qs, just PM me.

Thanks guys.
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http://gamesdreams.com/showthread.php?202154-A-Visual-Guide-to-Nemo-s-Reef