carbs and mechanical fuel injection are easy to rebuild, and easy to make changes.
efi is easy to tune, and has tighter control over fuel and ignition timing curves.
carbs and mechanical fuel injection require more steps to get the fuel curve close, and when you make changes to other systems, you need to go back and retune the fuel curve.
with carbs and mechanical fuel injection you can get close to the fuel curve the engine wants, but the system is not adaptable to changing conditions.
efi is expensive to set up, and requires a lot of effort to troubleshoot properly.
as to horse power, they all make about the same power when installed on otherwise equally built engines.
as to torque efi engines will have a slightly fatter torque curve due to the tighter control over the fuel curve.
as to fuel economy, efi thumps the others again because of tighter control over the fuel and ignition curves.
the biggest advantage efi has over the other systems is the flexible fuel capability that has been added in recent years. carbs and mechanical fuel injection need to be tuned to a specific fuel type, ie; gasoline, E85, straight alcohol, where as efi can have a sensor built in to determine the amount of alcohol in the fuel, and adjust fuel flow through the injectors accordingly.