Hey! I had this exact dilemma....wanted to do Scots Law but considered doing a dual-qualifying degree as it would be more 'unique'.
I asked a solicitor I shadowed in the Summer for her opinion because she did Law with English law at Aberdeen. For clarity, I'll insert her reply but basically she was saying now with the introduction of the bar exam, it is easier to dual-qualify once you have your degree and she would recommend going down that route instead.
Message from solicitor: "I only chose to do a dual qualifying degree as I wanted to potentially qualify down south. However, with the introduction of the SQE (legal exam in order to qualify in England & Wales, in case you weren't aware), you don't really need to do a dual qualifying degree anymore as anyone can sit the exam. If you are set on doing corporate/commercial law such as what my firm does, then I would suggest taking law with business/economics as you will have an edge with that. In other words, it was a little bit of a waste when I could have taken much easier subjects. You basically take the English subjects when you could have chosen any other elective (i.e politics, psychology which are of course much easier than a legal exam). However I enjoy the law and I was pretty good at essay writing, so I didn't find the English subjects particularly difficult, so if your interest is just in law, you could still take them."
It is completely up to you what you want to do! Why not apply for Scots Law at Edinburgh and then Scots with English Law at Dundee/Aberdeen and wait until you have offers? Typically, Edinburgh is more competitive so it's fantastic if you manage to get an offer and you would probably benefit more getting a degree at Edinburgh but of course, Dundee and Aberdeen are also great law schools. And your dad is right, a dual-qualifying degree does give you a flair but likewise, taking other credits (such as business or English) in first and second year can do the same in terms of making you more 'unique'.
Best of luck coming to a decision and keep us updated.
Rooting for you!