>Is there a comparison somewhere. I'm not only interested in the database engine, but tools and UI features as well.

There used to be a comparison matrix reachable from the MySQL homepage - but I have no direct link.

There are some sites giving an overview of MxSQL shortcomings, be sure to check them first.
MySQL has shown lesser scalability than PostGres in some tests mainly aimed at showing the scalabilty of WoodCrest/Opterons when using 4 double cores. Might be relevant if you foresee a DB hammered to the hilt - but I have not found current comparison (including numbers and methology) with the commecial ones, perhaps due to benchmark clauses in their EULAs.

Personally I wonder why you exclude DB2 from your list.

regards

thomas