Interesting analogy!! Just like: BIG FISH in small pond, or small fish in BIG OCEAN..... The hardest decision to make. But is a decision really needed??
If one dojo doesn't want you practicing at the other dojo, yeah, I'd say a decision is needed.
It does strike me that OP's knowledge of the conflict is second-hand knowledge (anecdotes told by friends). Not to say that they're not true, but it may be worth carefully gathering some first-hand information. People do change and they do move on, and it may be that the people whose attitudes were responsible for the conflict are no longer a problem. It may be worth asking at the southern school what the view is of training elsewhere. Also, if you do get a negative opinion, who is it coming from? Sometimes seniors can be extra-zealous about something that's really no big deal to sensei.