Found this at all3dp.com:
PLA (PolyLactic Acid) is a biopolymer, i.e., a biodegradable plastic. It is made from renewable raw materials such as cornstarch or sugarcane. Aside from 3D printing, it is typically used for packaging material, plastic wrap, plastic cups and plastic water bottles. It is considered to be more ecologically friendly than ABS Ė after all, itís made from plants.
ABS (Acrylonitrile-Butadiene Styrene) is an oil-based plastic. It is a tough material that can be used to create robust plastic objects for everyday use, for example in cars, electrical equipment or even in the popular Lego bricks.
PLA is more brittle and has a higher surface hardness. It is more prone to break when bent. Objects made from this material can be cut, filed, sanded, painted, and bonded using adhesives; treating them with acetone (for improving surface smoothness) is not possible.
When printed at the temperature recommended by the filament producer, ABS exhibits a superior layer bond. Objects 3D printed this way will be stronger and more impact-resistant. Therefore, it is better suited for mechanical parts and for objects that need to be weatherproof. Moreover, ABS parts are more flexible than PLA parts and tend to bend rather than break when under pressure. Also, ABS is better malleable, postprocessing is easier: The printed object can be cut, filed, sanded, painted, and bonded. And they can be treated with acetone to get a smooth and shiny surface or to weld two objects together.
To me, ABS seems to be the better choice.