Every freelancer starts by delivering work over email, and for the first few projects it is genuinely fine. You attach the files, the client replies, you send a revision. The trouble starts around revision four, when "the final version" exists in six different threads, the client is replying to the wrong one, and you cannot remember which file they actually signed off on.
Email was built for messages, not for managing a project with versions, approvals, and money attached. A client portal is built for exactly that. Here is the honest comparison, because email is not always the wrong answer.
Version control
Over email, the file lives in attachments scattered across a thread, and the newest is whichever one you can find. There is no single source of truth, and "use the latest" is doing a lot of work in that sentence. A portal keeps one place where the current version is obvious and the old versions are still there if you need them. When a client says "go back to the one from last week," you both know exactly which one that is.
Approvals and accountability
Email approvals are real but fragile. A "looks good" buried in a reply is hard to find later, and impossible to attach to a specific file version. If scope is ever disputed, you are searching your inbox for a sentence. A portal where the client clicks to approve a specific deliverable leaves a timestamped record against that exact version. That is not bureaucracy, it is the thing that protects you when someone says "that is not what we agreed."
Files and large deliverables
Email attachments cap out fast, so freelancers fall back to a Drive or Dropbox link, which means the work now lives somewhere else again, behind its own sharing settings the client has to navigate. A portal holds the files in the same place as everything else, with no separate folder to share and no "request access" email from the client who cannot open the link.