Is it better to negotiate at a dealer or use Carvana's fixed price?

It depends on how comfortable you are negotiating. If you are a confident negotiator with competing quotes in hand, you will almost always do better at a dealer than with Carvana's fixed price. If negotiation causes you stress or you tend to accept pressure tactics, Carvana's fixed model removes that risk. A third option is using a broker, which sources pricing across a dealer network on your behalf without requiring you to negotiate directly.