Hello Fabrice
Cisco Performance Monitor is not a replacement or an alternative to Netflow. CPM is an extension to Flexible Netflow, which itself is an extension to Netflow v9. Which you will choose depends on what level of monitoring you desire.
CPM is ideal for monitoring metrics for real-time applications. Metrics such as Jitter, packet loss and round trip time are all vital for such applications. CPM would be very beneficial if you have such applications, however, if you don’t, Netflow may be sufficient for your needs. You will have to evaluate this based upon your requirements.
I hope this has been helpful!
Laz