There is that. And then there is the far more fundamental principle/question, that has likely always existed, but the brexit issue has really hammered home. Is Scotland ever going to have any meaningful say in anything of signicance as a part of the UK? that really has been the SNP's raison d'etre, and it is what they are drilling into on the back of it. And it gets harder and harder to argue.
Once you believe the answer to that to be no, then it is a case of, is it worth accepting that, to be part of the union, whether it is for emotional/historic attachment, sociological, or economic reasons.
Brexit again touches all 3. As societies go, it is obvious they are pulling in quite opposite directions, and that is what the SNP are playing at with their theatrics of the candles, flags outside holyrood, but even the messages of inclusivity and welcome, in contrast to the outbursts seen across england. They are merely picking out the differences and parading them to the public. The economic case is one that people rightly will argue, and is yet to be made, and may well be the make or break of it all. Again, if brexit negatively affects everyone's econoomy, and given any feeling of above that it was forced on scotland, then that will probably be the focus, rather than the more concrete questions.
Re the emotional attachemnt, the narratives of Boris refusing what the elected parliament that represents the people is requesting, and even more broadly, the feeling of 'we dont want the moaning better-off jocks anyway, know your place etc etc' which is very noticeable in the media, both formal and social) is what will be lapped up by the snp.
So me, i can only see one direction for now, and those economic arguements, well who can say if they would be enough in the context of all the rest.