One of the most significant factors that make PCs stand apart from the competition is the design. Prebuilt systems like the Alienware Aurora R11 or Corsair One use unique in-house chassis designs you wouldn't be able to purchase when building it yourself. You can take some comfort in knowing that these systems were designed and built specially to house your configuration, though that can make upgrading more awkward later on down the line.
When we set out to choose our top choices of prebuilt gaming PCs, we look at almost every major manufacturer and system integrator to find the best combination of value, reliability, customer feedback, design, and performance for various budgets and needs.