Both are control panels for a web server: files, databases, mailboxes, DNS, certificates, PHP versions and backups, behind a login instead of a command line. The arguments between them are mostly habit, and the parts that are not are easy to state.
What is genuinely different
- Operating system. cPanel runs on Linux. Plesk runs on Linux or Windows, so a site that needs ASP.NET or MSSQL is a Plesk question rather than a cPanel one.
- How the interface is organised. cPanel separates the account from the server administration, with WHM over the top. Plesk puts both in one interface with different permissions. Neither is better; they suit different habits.
- Licensing. Both are commercial and both are priced per server or per account. On our shared plans the licence is already included. On a VPS or a dedicated server you buy it separately, which is why it is listed as its own product.
What is not different
Both will create a site, issue a certificate, make a mailbox, give you a database and a user, schedule a cron job, show you a log and take a backup. If a tutorial tells you one of them cannot do something ordinary, check its date.
Our answer
Every shared hosting plan here is cPanel, and the licence is in the price. We did not pick it because it wins an argument; we picked one so that every account on every server works the same way, which is worth more to the people we support than the difference between the two panels.
On a VPS or a dedicated server you choose. Buy the licence on the same account as the server and it renews on the same date, which is the only part of this that is really ours to make easier.
If you are moving from one to the other
Both can import from the other, and both do it better with the original server still running. Copy the site across, test it on the new panel while the old one still serves visitors, and change DNS last. The step people get wrong is pointing the domain first and then discovering what did not come over.