To me, this question isn't really about whether an electronically controlled throttle body is "better" than a carburetor because it's probably a wash in that regard. What EFI does offer is much more finite control over the entire operating range of the engine especially when the ECU controls the timing. Carburetors are much more coarse in their adjustabilty at least with 'normal' tuning situations which obviously leads to compromises. Like say you're tuning for max power at WOT - your part throttle drivability may suffer and vice versa - if you're tuning for economy, your WOT settings will be affected (generally). When you start getting into modified engines, it can be difficult to get a carb to be perfect in all scenarios.
Basically EFI allows you to tailor every point in the ignition and fuel curves for optimal performance. Does everyone who gets involved with EFI go to the lengths required to get their combo to that point? No. That's where you need to be honest with yourself - do you want to spend the time with the software dialing everything in to the best it can be or do you want the ECU to take care of it for you? It's hard to say what your results will be if you don't take the initiative and get involved with the tuning process. Theoretically there should be some overall improvement with EFI but it may not be noticeable enough to be worth while.
I went through the tuning process on my Coronet. I enjoyed it but it did take a long time to get it sorted out properly and the learning curve is steep. But once I built my own custom timing and fuel curves it really made a difference in the overall drivability of the car. I can say with 100% confidence it ran better than it ever did with a carb. I attribute that largely to the digital ignition and ECU-controlled timing but honestly, it was a huge overall difference. No gas smell in the garage, no pumping the throttle on startup and it even increased mileage.
Mind you, this was a basically stock 383 in a heavier car. It had #452 cylinder heads, factory 10:1 flat top pistons, factory hydraulic "335hp" cam", an Eddy Performer intake (which is basically a copy of the stock iron intake in aluminum) and headers. It was not setting any records and it was a struggle to get it to rev over 4,500 rpm but within that range it was good. It spent most of it's time under 3,500 rpm anyway. It was really fun to take on back roads and run it through the gears.
EFI is also a big investment that requires a lot of peripheral parts to make it work properly. The fuel system requirements can really add up. It's also not really worth skimping on the igniton because it basically defeats the main advantage of controlling the timing. And be aware the wiring in the car needs to be in very good shape or you will have all sorts of problems. If the wiring is a mess or even just old, don't even think about EFI until you get that sorted out. I rewired my entire car before EFI and it was absolutely the right thing to do.
If you drive the car a lot in many different scenarios and are willing to get involved with the software, I'd say go for it, it will be great. If you only take it out every once in a while just to putt round town or park it at a cruise night, it might not be worth the expense or effort.
