At least one spreadsheet out on the web uses a tail efficiency value that is more suitable to full size planes. So the choice made by the person that wrote up any given spreadsheet or online calculator would affect the results.

I'm going to guess that the reason for a higher tail efficiency value would stem from the higher Reynolds numbers of full size aircraft. So the ones that use smaller values for tail efficiency and generate a more conservative CG location would be the one to go with if in any doubt.

But I have to agree that other than perhaps serious 3D models where a given CG on the plans might be the sort of thing an expert pilot would choose I'd just go with what the designer indicates. If you have some concern over not being as good a pilot then shift it 2 to 3% of the chord forward as a starting point.