I know most of people don't know abut it, anyways I am sharing the information.
ABS is cheaper to manufacture and has bad side affects for example, if you place an ABS bath in front of a window it will start to go yellow and start to show signs of cracking, if you drop something in the bath and it chips, this is not repairable. The colour is also a bright white which will not always match your ceramic ware, most overseas manufactures use this product. Acrylic as used by UR Direct is twice the price of ABS but is not affected by UV light and can be easily repaired if neccessary, the colour will also match the rest of your ceramic ware (based on the colour being a white suite).