Yeah, Kev provided all the necessary information to answer the question.
I would also highlight that the reliability is SIGNIFICANTLY higher of a single speed bikes.
In my childhood, singlespeed was the most common and nobody was even thinking about getting anything else as it was enough. However, single speed might even have to be walked if you have to climb up the hill and your bike is heavy...
It's a compromiss, hope you get the point, and I didn't miss.