What’s better? A main email address with multiple aliases or a domain with multiple emails?

So the past week I’ve been going down this “rabbit hole” of learning how emails, domains, aliases work.

I want to open up a discussion and see which is better for my personal reasons.

Is having one “main” email address with multiple alias addresses better?

Or

Is having a custom domain with multiple emails better? More so, a centralized email with email aliases under the same domain.

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