NoSQL Tech Comparison Report
In the relational RDMS world, there are only a few companies who owns the majority of the market share. It is usually very easy to determine what technology to go with, depending on the budget and business objectives.
However, in the non-relational RDMS world, it is far more difficult to have a decision. There are plenty of variants, each having its own advantages and disadvantages. The following report from DBTA is a very good source to aid in their decision making.