With Altium 17, what is the result of placing and SMD Pad inside Solid Region?
Fills and solid regions will flood the area with copper, even if the net name doesn't match. Thermal reliefs are not created for pads that match the fill net name. When you run a DRC, error messages will show the shorts if the fill is contacting other nets. Be careful when using fills &amp; solid regions.
A polygon pour will isolate the pour from nets that are different and create thermal reliefs if desired.
Pours have one drawback. When creating multi-channel layouts, the copied pour will not take on the proper net name so you need to manually set the net name for each pour in the copied channels. Fills will take on the proper net name.