I created an HDA from a Object node and Houdini prompted me to “Create Subnetwork from Selection” before making the HDA. I declined because I didn't think it was necessary.

Later, while modifying the HDA, I frequently put the render flag on the wrong node which then caused the HDA to produce unexpected results. While looking for a solution to keep me from screwing up the HDA, I tried adding the Output [www.sidefx.com] node but discovered the it only works within Subnetworks [www.sidefx.com].

From experimentation, I also found out that making an HDA from a Subnetwork creates an HDA that can be used in a Geometry (SOP) network, while making an HDA from an Object creates an HDA that can be used in the Object network.

Aside from the above, what considerations should I keep in mind when choosing between Object HDAs and Geometry/Subnetwork/SOP HDAs?