Compare prices. How do you know their parts are any good?
Just assume when you purchase a Retail computer that it can not be upgraded in any way.
While you may not have the same choices upgrading a GPU and PSU, and some case mounted ports as you would if you got to pick a MoBo and case over the OEM one you get in a Retail build, you
can upgrade the HDD, RAM, various add-on PCI-E cards.
The second problem is when a retail computer has problems, how will you get it repaired? Will they come to your house to fix it or do you have to mail it somewhere at your expense?
If you get a computer from a Retail company, there is usually
some kind of umbrella warranty on the whole system, including variable coverage on Windows...some companies are better than others (sounds like Cyberpower may not be that great or convenient, but if you buy it at Costco, you can get their warranty). If you buy a Dell Business computer with ProSupport, they
will come to your house. But if you build it yourself, you get individual warranties from each component manufacturer, not the whole system.
You get to be Tech Support. I'm definitely not saying to
not build your own, but you'll either have to do your own troubleshooting, or bring it into a local shop during business hours. BTW, a local shop might be an alternative since they should back up their build
and give you flexibility in component choices.