When you have considered the possible feature interaction among the DBMS product features you are considering, you are ready to determine your critical features. If a product is missing even one of these features, you should not consider it. This list of critical features will radically reduce the number of products you are looking at. It's important to keep in mind that these critical features will apply only to your current application. Future applications may have a completely different set of critical features.
Every application is different.
In my experience with clients, I have never seen exactly the same list of critical features. Any product on this list has the features to do an adequate job for you. You might want to bring these finalists in for a final questioning based on the deep feature understanding you now have. And, you may want to ask them some questions about their business strategies, market segment, and financing. You should be comfortable with the company that makes the product on which you are going to depend.