Do you think you would ever want to use points from both contracts at the 7 month window? If so, having the same use year is an advantage. That assumes you would arrange to have the second contract added on to the original. That can be done (at least for now) with resale contracts if they are titled exactly the same, have the same use year and you notify the closing company and Disney that you want that arrangement.
If you have different use years, you cannot combine points from the two contracts to book a single night. You would have to transfer points between them. Doing so would use up your "one transfer pr use year per contract" entitlement for both contracts. It has been reported that MS is more lenient if you are transferring between your own contracts to make a reservation for yourself. However, IMO, one should not count on that to continue, especially if one or more of the contracts was obtained via resale.
It is simpler to have the same use year & contract (even if the home resorts are different), but it is certainly doable to have different use years and membership numbers. You will just have to be a bit more vigilant about managing your points.