What is the benefit of 220 volt supply over 110 volt or 440 volt?

The higher voltage will draw less current and need smaller wiring.

Thanks stratmando,
Then 440 volt supply must be better?

Problem is 440 is not available for Residential.
Transformer Primary needs to match available power source. 120 volts is most common, and can be plugged in most anywhere. 240 wolts would have to come from the panel, you wouldn't hook transformer to an existing Range or other 240 volt device, would have to come from Panel. Availability is a factor.

Thanks stratmando,
One more thing, is there any particular reason for the voltage to be
Multiple of 11?

Yes there is, and has been asked before: Look through a couple of these:
voltage in multiples of 11 - Google Search (http://www.google.com/search?q=voltage+in+multiples+of+11&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7GGLR_en)