Less bank accounts means less overdraft available, close your redundant bank accounts.
Option B
Keep credit utilisation low, keep your accounts.
Which is better?
Check how much your card lets you borrow each month (that’s your ‘credit limit’). Then, if you want to boost your rating even more, try to only spend a portion of that each month. It’s about showing you’re in control of your spending.
Black box number: https://www.moneysavingexpert.com/loans/credit-rating-credit-score/
Which is better?
You don't really know.