I found a couple of resources that may help you in the decision of starting 1 or 2 hives. Our recommendation starting 2 hives because no 2 hives are the same.
If one hive becomes queenless or is weaker than the other hive, you are able to borrow resources from the other hive in order to compensate for the weaker hive.
Resources like borrowing a queen, boosting up broad, needing extra honey stores, need eggs.
If you have one hive and your queen dies, you will need a queen pretty quit. Once you have a laying worker then it is difficult to recover from this event. Scrambling around looking to buy a queen bee can be stressful.
I found a couple of resouces to read up on