I'm looking to purchase a beginner motorcycle/bike. I would like something that has less maintenance / potential for issues.
Which one is less likely to be an issue in a bike - carburetor or fuel injection?
Overall, and especially on multi-cylinder engines, carburetors simply don't stand a chance.
Jets that may get clogged, diaphragms that may rip, and reliance on exact pressure levels all provide failure points. Unless the bike has some sort of automatic start assist, you'll also have to get used to using the choke to start the engine when cold. If anything fails, you'll usually have to remove the entire carb, and figure out what exactly failed, followed by a non-trivial amount of tuning / setting up to get it running again.
Fuel injected systems are effectively just a pump, a (or multiple) injector, some sensors and an ECU. If any of those components fail, it's usually pretty easy to find the culprit and simply exchange it.
Unless price is an absolute priority and the carbureted bike is much cheaper, EFI wins in every regard.
It is difficult to answer as potential problems vary.
A carb bike can suffer more from modern fuel degrading if unused for a while, leaving residues blocking jets. Needle valve can wear / stick causing flooding. With CV type carbs the diaphragms can perish. With multiple carbs they need balancing occasionally. But if used regularly then not a major issue, and some of these potential issues are likely to still allow you to limp the bike home.
With fuel injection systems they are generally reliable. A high pressure pump is required, and a healthy battery to run the pump to get the fuel up to pressure. The pumps can stick with residues of old fuel if unused for a while, but generally FAR less likely to happen than with a carb. Fuel filters are more critical. They are reliant on various sensors, but in general these are pretty reliable.
Overall I would say that injection is generally more reliable, but when it fails it is more likely to leave you unable to limp the bike home, and potentially harder for a home mechanic to fix than carbs.
For a couple of examples. I have a 1200 Bandit. This suffered from jets becoming blocked when not used for a while. Getting the bank of 4 carbs off this to clean is a pain of a job (due to the design of the bike) and fiddly. Cleaning them out properly can be a fairly long job.
My father had a Ducati Monster S4 which was unused for a while and the fuel pump stuck. This pump is inside the fuel tank, and difficult to get at (you need to remove the surround for the fuel filler cap, which is held in place by several tiny grub screws, then once that is out if you have small hands and arms you can just about reach the pump at the bottom of the tank through the filler cap hole). The pump worked after a bit of cleaning.
Go with a model that has a long run history with few changes. I have never had a issue with Harley Sportsters or Ninjas 650r. The bike that gives me the most trouble is a Yamaha, but that was because of heavy modification.the definition of hot rodding something is you are taking it closer to its mechanical limits so it becomes less reliable.Stick with long run, good reputation, do maintenance, don't modify... for a year.
I have a direct comparison, since I have two Honda Shadows, with otherwise very similar engines, but one has fuel injection, one has twin carbs. I think there's also a single carb version...
The fuel injected one has always been perfectly reliable. At the end of each season I run the tank down to near empty, but I don't think there's any procedure to completely empty the system, and it's always started well, even in low temperatures.
The carbed bike, though it is older and had been a little neglected before I got it, has been far more problematic. Uneven fueling was traced to a sticking needle valve in one of the carbs, though the mixtures are't perfectly matched (and are intentionally mismatched per factory settings for some reason). Jets have gummed up, and though I haven't experienced it, sometimes the throttles of the two can get out of sync - there's a linkage between the two with adjustment screws. At the end of the season, I drain down the tank, and there are drain screws on each of the float bowls to empty them too. Hopefully now that I've cleaned all the bowls, jets and passageways, it won't clog again soon.
It hasn't been much of a problem getting it started except when something was amiss, but needs to run a minute or so to settle down before setting off. The injected bike can be just a matter of pushing the starter, then setting off immediately.
The injected bike, therefore is far lower maintenance, and more reliable. The one thing I'll say against it is that the idle speed, which is fairly low even when cold, makes it easier to stall, the carbed bike obviously has an idle lift with the manual choke, and the idle seems to be higher anyway, so it's easy to creep along at idle in stop-start traffic.