Hi BigMag,
I use both at my current site. The online system is written in Cobol and the majority of the reports are written in Focus.
My personal opinion:
Cobol is slower to develop, particularly if you are talking about simple reports, where Focus is streets ahead. This is the only area where Focus wins.
Cobol is easier to understand and maintain, better structured, and quicker to run. The way Focus programs have been written here, they tend to be monolithic, and often repeat sections of SQL in order to mix and match the data they want.
No one here has attempted to use Focus to update our DB2 tables. Although I believe it can be done, this has steered clear of it, so I can't really comment, other than to say that Cobol can and does this with ease.
In summary, if you have simple reports, use Focus. For complex reports, and online processing, use Cobol.
As I said at the beginning, this is just my opinion, based on usage of both languages.
Marc