Difference between beneficiary and successor in TFSA and RRIF

Both beneficiary and successor (B & S) are heirs.

B & S can be assigned in both RRIF and TFSA, with slight differences between the two programs.
A successor can only be a spouse, while other heirs must be beneficiaries. You can assign both a successor (e.g., 40% to the spouse) and a beneficiary (e.g., 60% to the child).

To keep it simple, here’s the difference:
If the husband dies and the wife is a successor, the entire TFSA balance is transferred to her TFSA, regardless of her limit. For example, if the wife has $31,000 in her TFSA and the husband has $10,000, her TFSA will become $41,000.
If a beneficiary is assigned, they simply receive a check for $10,000. If the beneficiary has room to contribute to a TFSA, they can deposit the amount. If their TFSA limit is reached, they cannot contribute.

If the wife is a beneficiary, CRA may allow transferring the deceased spouse's (e.g., husband’s) TFSA to the surviving spouse (wife) by submitting a request to CRA.

Difference Between Beneficiary and Successor in RRIF.

If you have a RRIF and a significant age difference with your spouse (5+ years),
If you're older than your spouse (or vice versa), it's better to name your spouse as a beneficiary rather than a successor in the RRIF. Why? If a successor is named, the surviving spouse will continue to receive payments from the RRIF based on the same rules as the deceased. For example, if the deceased was 75 and the surviving spouse is 68, the surviving spouse will continue receiving RRIF payments as if they were the deceased.
If a beneficiary is named, the RRIF can be rolled over into an RRSP, and no withdrawals are required until age 71.