What is the advantage of 50 Hz ac to 60 Hz ac system?

There really isn't that much of an advantage. Since many countries work with both frequencies, many appliances, especially computers, have the option to run at 50Hz or 60Hz. You will know this because in the back of the unit where the power supply is located, there will be a switch that allows you to change from 50Hz to 60Hz.

If you have any type of equipment that does not provide the option to change frequenies, but the equipment was made recently (in the last year), you can safely run it at either frequency. If your equipment is older, you may want to contact the manufacturer to see if they have any special transformer or electronic device that can be connected with the electronic equipment to allow for such a difference in frequency.

The only real difference you may experience with certain appliances that run two-phase or three-phase motors is extra heat buildup while running at 60Hz.