Should I hire a freelance Magento developer or an agency?

Hire an agency when you need five or more parallel workstreams with a project manager coordinating them. For everything else, a senior freelancer is usually the better deal: the certified developer you talk to is the one writing the code, there is no agency markup, no hand-off to a junior after the sales call, and no ticket queue between you and the person fixing your store. You get direct WhatsApp access and one accountable name. That structural difference, not effort, is why the same scope often costs 2 to 4 times less.