EFI is way better. Way more tolerant. Most EFI set up's are 'closed loop', there are O2, Throttle Position, MAF/MAP sensors to monitor air going in and the O2(Temperature and speed too in some cases) levels of air going in and the O2 content of air going out too. All this means is that there is constant adjustment to the amount of fuel input into the engine and monitor and adjust ignition timing, so you get a level balance of good fuel economy and power output.
Something you should note that EFI set ups produce more power and torque, and something that I like about aftermarket EFI systems is that I can 'tune for' peak power, peak torque or balance the two - and it is way easier as I have all of the data in front of me, in real time. I can do the same with a set of side drafts, but I need to tune and drill(I have really small drill bits for this) fuel and air jets to get the car to run in various environments without needing to change the jetting of a carb.