I like the keys. The key has the locker number on it, so you don't have to remember anything. And there's no way to screw up setting the pin because of a language barrier, since there are basically no instructions needed for key lockers. FWIW the key lockers are more common in Japan as well.
I agree with you with regard to convenience, but what about security? For the application of railway station lockers, one can assume that they will be under CCTV or other monitoring. I am no expert in locks, but presumably an electronic lock, whilst perhaps less secure overall, is harder to break without obviously looking like one is tampering with it. This is in contrast to a conventional barrel lock, which can be picked with tools that look enough like keys not to arouse suspicion from a distance.
