The primary difference between 50 Hz (Hertz) and 60 Hz (Hertz) is, well, 60Hz is 20% higher in frequency.
For a generator or induction motor pump (in simple terms) it means 1500/3000 RPM or 1800/3600 RPM (for 60Hz). Lower the frequency will be the iron losses and eddy current losses. Lower the frequency, speed of induction motor and generator will be lower.
For example with 50 Hz, generator will be running at 3000 rpm against 3600 rpm with 60 Hz. Mechanical centrifugal forces will be 20% higher in case of 60 Hz (rotor winding retaining ring has to bear centrifugal force while designing).
But with higher frequency, output of generator and induction motors will be higher for same size of motor/generator because of 20% higher speed.
50Hz vs 60Hz on efficiency
The design of such magnetic machines is such that they are really one or the other. It may work in some cases, but not always, and to change between different power supply frequencies will certainly have an effect on efficiency, and may mean de-rating is necessary.
There is little real difference between 50 Hertz and 60 Hertz systems, as long as the equipment is designed appropriately for the frequency. It is more important to have a standard and stick with it.
The more significant difference is that 60Hz systems usually use 110V (120V) or thereabouts for the domestic power supply, while 50Hz systems tend to use 220V, 230V etc. for different countries. This has the impact that house wiring needs to be twice the cross section for the 110V system for the same power.
However the optimum system is accepted as around 230V (wire size and power required versus safety). In most of the US the 110V power system is in tandem with the 240V US system that provides for the higher powered appliances like stoves and clothes dryers, while 110V does wall outlets and lights. Hardly an issue of the appliances nowadays.
Is 60Hz better than 50Hz?
It is no big difference between 50 Hz and 60 Hz, nothing is bad or good basically. For independent power equipment like ships, aircraft or isolated area like gas/oil installation, any frequency (like 400 Hz) can be designed based on suitability. From an overall perspective, we can't say 50Hz is better than 60Hz or not, there is no difference.
The main issue is the fact that there are two power supply standards. This means that links between transmission systems that run on different frequencies require DC links between them, or simply using a frequency converter to change 60Hz to 50Hz.