Neither is universally better. The best choice depends on its end-of-life plan.  Post Consumer Resin (PCR) is better for creating a circular economy by giving new life to existing plastics that can be recycled again, but still requires proper recycling at the end of its life. Compostable plastic is better if it can be sent to a facility to be broken down into organic matter, but it requires specific composting conditions and can't be recycled with conventional plastics. There are very few facilities that can compost dog waste separately.