Why does the USA use 110V and UK use 230-240V?
You should not be surprised that they use different voltages and frequencies, you should be surprised that there are only two big voltage/frequency standards.

When electricity was first introduced each producer provided a different voltage and frequency (or even DC instead of AC). Gradually producers merged, governments set standards, and market pressure demanded that appliances could be used everywhere. This lead to the current situation, where the pressure for a world standard is counterbalanced by the invested interests. 

For the same amount of energy 110V requires more current, hence thicker wires. 230V requires better isolation. In some rare situations 220V might be more dangerous to touch.

I don't think 50 or 60 Hz makes any significant difference. (An iron core for a transformer might be a little smaller at 60 Hz. But iron cores are soooo last century...)