In which class of element is there a greater range of properties, the metal or the nonmetals?

All metals are good electrical and heat conductors.

With non-metals you have graphite as a good conductor, several semi conductors such as silicon and numerous non-conductors.

At STP, metals only come as a metallic (funnily enough) white coloured solid apart from mercury, copper and gold.

Non-metals come as a gas (eg helium, hydrogen, etc.), liquid (bromine), and solid (eg diamond) at STP and a variety of colours. Yellow sulphur, green chlorine, purple iodine, etc.