Personally speaking, all these targeting options have their own pros and cons. For example, in custom audiences, marketers need to insert at least 500 phone numbers or email ids in order to create a custom audience. Below that number, it’s not possible to create a custom audience. But this targeting technique has the highest conversion rate. Hence, depending on the brand, product or service, marketers need to identify which targeting platform, technique or a mix of both, can be used that can give them the best results.