the problems only arise when you’re also accessing the documents through, say, your ipad or similar- from the native dropbox / drive app the graffle document will be recognized as package and therefore opened to reveal an xml file among other things…
The route Omni chose to circumvent this is called OmniPresence. All documents in there can be directly tied to the specific mobile apps and syncronized/opened accordingly.
Apart from the mobile caveat, you’re absolutely free to pick your preference in terms of cloud syncing. For the biggest flexibility (who knows when you’re gonna need that sketch on your ipad ASAP ;-)…) I would nevertheless recommend OmniPresence.
