Actually the answer to the question in this blogpost's title in the C21 great scheme of things probably matters little to what is now the UK given thankfully that we are no longer "a great power" as we were in say C19.
If the Scots vote for Independence they will still doubtless be friends but currently and quite unfairly far fewer Scots voters are required to elect an MP to Parliament in Westminster than are needed by voters in England and Wales - (apologies to Northern Irish voters but I am less sure of the electoral position there).
The disproportionate number of voters per MP issue gives rather more power to individual Scottish voters than to their counterparts in England and Wales.
Furthermore the same issue results in the Labour Party and SNP voter in Scotland having rather more Westminster MPs per head than their English and Welsh counterparts.
The fact that the Tories have lost popularity in Scotland is their problem but the fact that voters in Scotland are given more MPs per head than those in the rest of the UK is patently unfair. For that parochial reason alone I would not feel too unhappy about Scotland breaking away from the UK. A likely outcome would then be that the vote of one man or one women would be worth approximately the same in the remaining parts of the country. True at present (new UKIP voters apart) that would make the Labour party candidates less likely to be elected in sufficient numbers to form a government but the whole voting process would be fairer as the broad similarity of the worth of one vote throughout the remaining UK would not give an artificial bias in favour of one or other of the parts of the country, as occurs now,
The above point would be capable of fair resolution within the existing UK but naturally enough, those political parties which currently benefit Westminster-wise from the disproportionate weighting in favour of the Scottish voter, decline to agree to any change.
In the light of the above rather parochial point, if the Scots vote 'yes' to independence, the electoral position for the rest of the UK should become far more balanced and fairer though in the world's terms both countries would probably become less politically significant. That may however be no bad thing.
We might subsequent to a 'Yes' vote even have the remaining parts of the UK electing to quit the EU with the Scots seeking to join, which would be rather interesting.
The above views are very much 'from the head'. 'From the heart' however I hope that the Scots vote 'no'.
A yes vote in Scotland could also have interesting side effects on the Basque regions of Spain (and France?) which have had a yearning for independence but that is another issue.