I too generally have preferred multiple subs, especially when crossing to small (bookshelf type) mains.
Driver Xmax and surface area will not be the same. Depending on how you plan to integrate the subs, that may not be a negligible difference. An 18” driver will offer ~10-12% greater surface area than 2x 12” drivers.
In your case, without knowing the specs for either model, I’d still be inclined to use two smaller subs vs. one bigger sub (again, especially with small mains and with music being a strong use case).