They provide mostly non-overlapping features. Stripe = get paid. Plaid = connector into banking data (transaction history on a checking account, or the account # itself, for example). So, if you need to accept payments, or send money, you'd lean towards Stripe. If you instead wanted to get access to a user's financial data, such as if you are writing a budgeting app or personal financial management application, you'd lean towards Plaid.