Your assumption is correct, the page property should override the dynamic property in that case.
If there is a scenario where that doesn't happen I would consider that a bug, and would be grateful for any reports on how to reproduce the fault.
EPiServer development team
What Per says is true. :) I know this is documented "somewhere" that I've seen in the past few days though I can't seem to recall where at this moment. It's also part the EPiServer Developer course. In any case, the following SDK page suggests the flow of logic when accessing a property in the section "What happens when you access a property?"
when there exists a dynamic property and page property with the same name, is there in CMS5 a predictable behaviour (by design) for what will be selected?
I've had some trouble with this earlier in EPiServer 4.
I assume and hope that the page property will override the dynamic property if it is set but need a confirmation that this really is the way it is designed.