People people people. A 1000watt light draws 10 amps PERIOD! 120 or 240 it doesnt matter. 120 draws 10 amps across 1 line and 240 draws 5 amps across two lines. So you still have 10 amps!!
240 wiring allows you to run smaller awg wire to do the same job. It really depends on how you plan to setup your house. If you want to do 2-1k lights per room then you would need to run a 12-10awg wire "the wire will have 4 leads in it not 3!!!!" to each room. 12 gauge wire would give you a 240 volt load capability or around 2500watts, a 10awg wire would get you around 3500watts.