You do not need 'dual voltage' for laptops, they only run off 14 volts maximum and this is transformed from 110 or 240 volts by the laptop. You may have to turn a small switch at the rear of the laptop from 240 to 110. You will need an adaptor plug but most laptops come supplied with UK and USA plugs.
Personally I would go for Dell as you have the worldwide warranty and you pay a hell of a lot for the Sony name but if you are a fashionista, the name may be worth it. IMHO Dell lappies knock spots of anything Sony can conjure up.