Hello Luciano,
I don't have a full grasp of the new stuff introduced into MonetDB in the last year, but as far as I know there are still major differences between the two systems for me the most important is scalability. Vertica has no single point of failure when working as a cluster. However the CE version is limited to three nodes, so scalability is also limited in that case.
Vertica relies heavily on projections as a way to improve performance. If your data model is relatively stable it is something fairly easy to use, but if your data model changes at a high rate you will have a considerable amount of additional work managing the projections. Also if you use many projections they will hurt your DML statements performance.
MonetDB feeds on CPU and has no boundaries for its appetite, consuming as much resources as possible in order to respond to a single statement. That can be very good or very bad, it depends on your use case. Vertica has resource pools that are used to regulate the stuff (IO, Ram, CPU) that each query is allowed to use.
I don't know your use case (and that is crucial for a good advice), but if you are considering a scenario where you have a single machine for the database system, then go with MonetDB without any doubt. It is just faster and simpler.
