I suggest to set it up new... so that things are clean at the start.... then you can verify and move things , by moving you can segregate and sort things to the right place from start itself...
You won't get a clear answer here. There are proponents of both. I am of the view that if your current system is working well, you can very likely just use Migration Assistant and everything will work fine. I have done this many times and never had a problem.
There are others here that insist starting new is the only way to go.
IMO, just migrate and it you have trouble you can always start over fresh.