First, can you default a form field through Developer Mode/Customization? If you can, what do people think is better, through a customization or through a BPM?
I know how to do it through a BPM, but had the question pop in my mind today about doing it through customization.
You can definitely default a field form via form customization. I use both to be honest. If the data MUST be correct and in the dataset, I use a BPM.
If it is more for reference, I feel comfortable using a form customization to do so.
A BPM will run no matter where the object is called from: the UI, Service Connect, REST but the Customization will only run in that particular UI. So I like to put data-oriented things in BPMs and UI things in Customizations.