Raid controlers what is the beter choice ?

Hello I have a question. What is the difference between Intel motherboards with integrated raid controllers and let’s say for instance the raid controllers on the lowest class of servers by HP. Let’s take for example HP ML110. The Intel motherboards are not specifically designed for servers and are desktop motherboards, let’s take for example INTEL D915PBL. Does the raid controller on the Intel motherboards offer less reliability, considering that the HP ML110 has an integrated Adaptec raid controler. If the need arises is it a better choice to use an external raid controller on a simple Desktop motherboard.