#1 reason for EFI: Today's gas sucks and nearly boils at room temperatures.
I have carb'd and injected vehicles. All my carbs suck, regardless of ethanol or not. After being parked hot, fuel boils away - even with an electric pump to refill the carb, the excess fuel in the engine causes long cranks and hard starts.
Letting a carb'd engine sit, or being stored for any length of time also always causes issues for me. Either with plugged passages, or failed parts/gaskets/seals. I've spent more in replacement carburetors and parts in the past 5 years than I have on oxygen sensors (none of my other sensors have ever failed). I have an offroad motorcycle that every season, regardless of how it's stored, needs the carburetor removed (no small feat!), cleaned, roto-rooted, and re-assembled. Even then it takes 20-30 mins of idling before it'll take throttle. Once it runs, it's great, most of the small running issues self-correct, but it can take several hours of running for fresh fuel to wash away the gunk of the fuel that's evaporated or corroded something. I still don't know how far a tank of fuel will take me on that bike, because I wind up spilling enough with every carb removal that I'm sure it has an impact. As a result, it doesn't get ridden near as much as it should.
Failed accelerator pumps and corrosion debris causing issues is a seasonal occurrence for me. It sucks! I hate smelling like fuel, and yet every one of my carb'd engines (and I have no less than a dozen on my property) requires some level of dismantling and poking about in order to make them run if they've sat more than a few days or a week. Doesn't even matter if I drain them first - without fuel present, condensation will cause corrosion issues and I'm still left smelling like gas after scrubbing and poking.
Just this weekend I had to fire up a carbureted mower at another property of ours. Been sitting with the fuel valve closed for 4 months - carb was run dry after the last use. Very little fuel in the tank, left in a conditioned space. Filled the tank with fresh gas, opened the valve and let the bowl refill. Took 1/2 an hour to get it started and running. My back and shoulder are wrecked from all the pulling. This mower has maybe 12 hrs on it - not even to it's first oil change. When used once a week, it starts on the first pull every time. But more than that, and the chance of success shrinks exponentially. I expect it will need a new carb by next year. Same with both of my 4 stroke weed-wackers this season. Serviced and stored dry for the winter. This spring, I spent hours getting them started and de-gunked.
At the other end of the spectrum, my EFI motorcycle fires right up (after replacing the battery), the EFI side-by-side fires right up, all my EFI cars (several of which are stored for the entire winter) fire right up. No faffing about with dumping fuel into the carb to loosen gunk and coax the thing back to life. No dealing with it popping and farting as it warms up. No dying at the stop light for the first few days as things start to work again.
This isn't the carburetor's fault, either - it's the fuel. It sucks. But apparently I can't get fuel that isn't garbage (even the ethanol free is garbage) so it doesn't matter.
Wherever possible I buy or convert to EFI because it just works. It doesn't leave my garage smelling like gas. It doesn't leave ME smelling like gas after having to dick around with it either. The worst failure I've had was an oxygen sensor that failed over the winter due to condensation. $40 and 30 mins later I was back on the road, and didn't smell like gas.
I think most people over-state the complexity of EFI. There's only a few sensors and they're all relatively cheap. TPS, CTS, MAP, IAT, and O2 - that's it. The cost for most of those is under $20, except the O2 sensor - and a well-tuned system could run without it. Not well, but well enough to get home or get to an auto parts store. When I have an issue with a carb'd engine, I have to check the pump, the bowls, the floats, the accelerator pump, choke, power valves or other diaphragm operated guts. Once I crack it open, I'm in for at least $20 in gaskets at some point - they'll re-seal long enough to get home, but will almost always start leaking shortly after. I also have to order those parts since few places carry them these days. I can get any of my EFI sensors same-day, but carb parts are a week away. Even then, I have a 50% chance of the ordered parts not being right for my carb, or being the wrong part marked as the right one... ugh.
My old edelbrock carb on my dart was replaced by a fitech. The edelbrock was OK so long as the engine was running, but I could never get it perfect either. I could either have a good cruise mix, or a good WOT mix, never both. So I could have an engine that wouldn't overheat on the freeway, or I could have an engine that didn't ping at WOT. I spent probably 200hrs tuning that thing even with some professional help. Never could get it good enough for my uses. It's not because carbs are impossible, but my combo at the time had some significant challenges (318, big cam, high stall, 3.91 gears, headers, living in the desert) and the edelbrock style carb was just not well suited to it. I could get close on the tune, but never 'right'. No matter how well it could have been tuned, there's no way to stop it boiling fuel. I had an airgap intake, .250" thick insulating spacer, 1" open aluminum spacer, and still the carb was too hot to touch when I shut it down and I could take the top off the carb and watch the fuel bubble and boil away. I could wait a minute, then take off my air cleaner and watch fuel vapor rise from the vents - no matter of tweaking the timing helped either, I literally tried everything from 5deg BTDC to fixed at 35. The fuel boiling was the final straw - having an engine that would wear the battery down trying to get fuel back into it meant I'd be walking at some point. I drove it less because I never trust it to restart after shutting it down, and would purposely only take it when I knew I'd have at least 1hr between shutdown and restart.
Within 2 weeks of installing my Fitech, I had a car that would start every time, would go WOT w/o leaning out, and would cruise all day and stay cool too. It may be more 'complex', but I drive it more now and don't worry about having to restart it while out and about. So far, the only issues have been user error. In both major cases, it was my own stupidity that caused the problem. In both cases I had high-current 12v+ wires that got shorted by the clutch linkage. One caused fuses to pop randomly while shifting. The second was such a drain that it melted a ground wire and would drop the voltage until the ECM shut off. Even a carburetor will fail to run given that kind of dumb.
All that said, I don't blame anyone who wants to keep their carburetors. They're initially cheaper, and if a person understands their function they can do great things with them. The type of fuel a person has available and the conditions they operate in may not make EFI as much of a 'requirement' as it is for some others. For me, it frees up time I'd rather be putting into other fixes/changes I want to make. I'll also be using the same edelbrock I took off my dart when I replace the 318 in my 4x4 because it won't have the big cam and high stall and other challenges the dart did when it wore the edel. But the 4x4 only gets used a dozen times a year, I can't justify the cost of EFI vs a carb I have on the shelf.. everything has it's place. EFI can be just as reliable, and to some of us are even simpler than a carburetor is. I find it easier to make tuning changes, even if knowing WHAT to change is more difficult than it is with a carb - it's a tradeoff.
I honestly don't think anyone can make any blanket statements about either system. Those that think they're going to drive their carb'd cars after the chinese nuke us are in for a rude awakening too, LOL.
