This completely depends on what somebody needs. Not one service is better. Dropbox is a storage drive in the air. iCloud is a synchronization tool. iCloud is my preference sync it does the work for me, but other people like Delphic since it provides a way to store files.
I have used them all from Dropbox to Skydrive to iCloud to Wuala back to Skydive (After getting my 25gb of space!) to google drive and finaly back to Dropbox. It just works better even thought you have a small space...
I use both equally and they each excel at their own aspects. Therefore they should not be compared. iCloud stores my app data, iWork documents, contacts, and calendar for syncing across my Mac and iOS devices. Dropbox is cloud storage for photos, movies, and other miscellaneous items. Both are great services in their own right.
iCloud for Apple stuff like app data and backups, and Dropbox for actual files. iClous doesn't easily let me just dump a file into it for later viewing on a different device.
I tend to use Dropbox more, i already have 9.85 GB of space in it for free... in iCloud, 5GB is the max and you cant go over it. That being said, I still use iCloud for the backups, so you cant compare it there as you cant do that in Dropbox. My overall opinion is Dropbox is better, but iCloud can still be used
I use iCloud, for just basic needs of syncing Contacts,notes,bookmarks and stuff like that it certainly works.
This is an apples to oranges comparison (no pun intended). They're both a round fruit, but they're not the same thing. As other people mentioned, iCloud is a sync service whereas Dropbox is just cloud storage. A much more appropriate comparison would be iCloud to Google Drive.
