Question: I am a bit confused when we should use power net in the schematic capture versus a normal net.

For example, if I place a 3V3, I would use a power net, however I see sometimes some schematic where some net/node for tension consideration which are placed with normal net. 

Example:

[![enter image description here](https://i.stack.imgur.com/xKkmA.jpg)](https://i.stack.imgur.com/xKkmA.jpg)

Answer: 
This doesn't really depend on the type of the net but more on your project type. For a "normal" project which is usually a hierarchical type, your power nets will be global (across all schematic sheets) whereas net labels are only local. This helps with quickly deciding if a net is used in multiple sheets or only the one you are currently looking at. This can be changed in the Project options -> Options dialog, but usually this is set to "Automatic".

[![Project Options setting (see red section)](https://i.stack.imgur.com/TwZvO.png)](https://i.stack.imgur.com/TwZvO.png)
I assume that net +VDD\_SNVS\_CAP only connects between IC pin G9 and C143 - if so, it should be a "normal" net. Just because the net name "looks like" a power net name, doesn't mean that it is really a global power net.

The +3V3 will, I assume, be connected to many things throughout your design, so should be a Global Power net.