It really depends on the car. Fuel injection can be a definate advantage in a performance situation, and it may be fairly easy if there are kits available for that particular car/ engine.
On the other hand, If you have a good running car with a carburetor and are not trying to squeeze every last ounce of power out of it, then you're probably better off keeping the carb. It would probably take more time, effort and cash than it would be worth to try to engineer a fuel injection system and get it set up right.
For an everyday driver, the original carb setup will be every bit as reliable and efficiant if properly maintained, and there are other people out there who could help you fix it and know the common problems. (not so with some One-off special setup that someone built).
But that's just my take.