What are the issues of my spouse and I having separate accounts vs sharing the same account?
Having the same account allows you to both have the same billing date and use the same payment method. Having separate accounts (you can use the same credit/debit card on both accounts) allows each of you to be your own “account owner” making phone changes easier.
There are no financial advantages to either.
Drilling it down a little more, each account has an account owner. This specific user / email can access all account features such as changing plans, viewing call longs, changing payments cards seeking support from Republic Help.
Having one account means simplicity as you only have one bill, one place to view everything, and one place to change things. However, if you need to change the plan for example, you need to log in with that one email.
If you have two accounts, each phone is kept separate but you also have to remember two different emails / passwords.