I intend buying a siliquartz kitchen sink (a form of white plastic) and wanted to know if it can be kashered for Pesach, or if it would be better to buy a stainless steel sink.

Buy stainless steal. A siliquartz wiil have to be cleaned and covered for pesach, Also before YOU USE YOUR NEW SINK POUR OVER IT BOILING WATER because the sink is polished after it is produced and the polish may have a non kosher ingredient and therefore requires a koshering procedure. esw