It's clear from tiffanyh's comment that the question is about the mail/calendar/address book part. Though, I cannot give an answer to that question. From my experience with a personal account, I can say that Fastmail permits much more customization.

We do have file storage via WebDAV or ftp, though it's not as full featured as companies that specialise in it. I wrote that up last year as well. It works OK, though it will be nicer one we spec out jmap file storage api.