I have 1Password on my iPad and my PC, both synced to Dropbox.
However, if I remember correctly (before I installed it on my PC), when you link the iPad 1Password version to Dropbox, Dropbox creates a folder called something like "1Password.agilekeychain. Inside that folder is an html link. If you open that link, you are taken to the 1Password sign-in (on the web). You sign in and you can see what is currently in Dropbox/the iPad's 1Password file. I've got my iPad (and PC) on automatic sync, so it's always up to date.
Another nice thing about it is that you can access Dropbox from any web browser and get to that folder or you can access that folder from your PC.
What I'm saying, ultimately, is that you don't have to have both - but I think you do have to pay to have both. It's been so long that I don't remember, sorry. I do like having it on my PC too (as you can use it for browsing and such on the PC and have it auto-linnk to the account/iPad).
Anyway, enough rambling. Hope this helps in some small way.
Marilyn