230V 50hz as used in Europe has a few advantages.
1) Any modern outlet (13amps(UK)-16amps(Europe)) can easily and safely supply at least 3000W making it ideal for portable heating, electric kettles, esspresso machines, irons, high powered vacuum cleaners, washing machines, dryers etc etc.
Many EU countries go one step further and hook cooking and heating appliences up to 380V 3-phase.
Homes may also be supplied with 3-phase with different circuits taking 1 phase + neutral (220V) to balance the load.
2) Because of the higher voltage cabling doesn't need to be quite as heavy.
3) distribution networks are not quite as transformer laden as they are in the US. Local distribution in urban areas can be done at the 220/380V supply voltage distributing power to an entire block / street from a single large transformer (substation).
Rural distribution is, at least here, similar to the US though (i.e. dependent on lots of local pole top transformers)
The US system has the advantage of using lower voltage (110-120V) which is, arguably, slightly safer. With the option of using 240V for heavy appliences, like dryers, as it's a 3 wire system.
However, both 110 & 220V will do a very nice job of killing you. (Bare in mind that early electric chairs operated at 110V!!! albeit DC) It all depends on how much current passes through, where it goes en route and for how long.
Modern RCD (Residual Current Devices) and equivilants in the US have made the chances of surviving a shock from either system much better.
As for the 50 or 60 Hz question:
The US settled on 60 Hz.. Fits nicely into the system of seconds, mins, hours.. 1/60th of a second = 1 cycle.
The Europeans went for an almost metric frequency basically.
The current oscillates 100 times per second (completing a full cycle 50 times per second)
giving you a frequency of 50Hz.
Nice round number.
It amazes me that the entire European area managed to pick 50Hz.. Imagine if every country had gone for a different frequency!!
However, there is really no advantage to either 50 or 60Hz they're just 2 standard frequencies adopted as conventions.
