Yes, foot retention is great if you want to spin for efficient power. All I'm saying is that if your bike has both front and rear brakes, you do not need foot retention. If you have some very steep hills and feel like your feet are going to fly off, then you might want to slow down a bit or get some foot retention. Conversely, if your city has a lot of steep ups and downs you might prefer a singlespeed. Or maybe you need to get a bigger chainring for a bigger gear inch ratio.

There's many, many options when cycling and you've been given lots of good advice here. Now it's up to you to decide what suits your needs and preferences best.