Mangle or firewall rule

RouterOS General
1

I’m going to restrict access to a specific destinations based on source Mac address. I have two solution.

  1. using mangle for marking connections and Policy Base Routing
  2. Restrict access with some firewall rule and without mangle and Policy Base Routing
    Which one is better?
    Which one is more resource intensive?
    Which one is suitable for rb450 or rb750 routers( routers with one core cpu)?
2

If you use RAW the cost would be the lowest.

3

Raw has unintended consequences if used improperly so get advice before implementing.
Mangle would eat up core I think more than a firewall rule.

What is the issue that you are trying to prevent??? that is the more important question to answer and will get you more optimal answers.