Avalon bus - what makes it so special?

Avalon bus is designed for FPGAs. It's resource utilization adapts to the complexity of the configuration of your bus.

As far as performance, fmax is usually determined by the components you've got connected and how. Latency can be extremely low (like 0) depending on the components in question.

What you ought to do is compile a few simple systems and look at the resource utilization for yourself. Or just compile some of the reference designs and look at the resource utilization.

Jake