What's the motivation? Either should produce the same power if properly selected for the application and tuned. In addition to the carb, you'll need a new intake manifold.
Personally I prefer Holley's because I'm most familiar with those. If you're putting on a mostly stock 400, a 750 vacuum secondary would be the best choice. For an intake, I'd suggest an Edelbrock RPM if it'll fit under the hood with the stock air cleaner setup.
