Who has the best online digital storage?

I’m faced with programs like Zumo Drive, Dropbox, Central Desktop, etc. and I don’t know how to choose which is best. What I need is reliable, secure, and remotely accessible digital storage system that anyone from my organization can obtain files from. The idea is to create an online “office.”

We’d also like a program (..they may be one in the same, I’m not sure) that allows two or more people to work together on a document at the same time while in different places.

Any ideas, or experiences you have with such programs that you could share would be great.Thanks!