Waste plastics are low-value waste; thus, achieving high-value recycling is the most desirable goal. Scientific methods are required to evaluate the environmental benefits and support the technology optimization and market selection of waste-to-energy technology for plastics. This study selected catalytic cracking and incineration power generation of two typical examples of waste plastics energy technologies as the research objects, established a full life cycle assessment model, and used the mid-point method to analyze and compare the environmental benefits of the two technologies. The results showed that catalytic cracking technology is more environmentally friendly. The sensitivity analysis showed that the treatment units had a high impact on the results; process optimization predicted the efficiency of technology optimization and advocated future technological developments to explore the direction of using clean energy, upgrading equipment, and updating catalysts. The results of this study can provide ideas for the optimization of two kinds of waste plastics energy technology. In addition, the comparative data analysis intuitively demonstrated the advantages and disadvantages of waste-to-energy technologies and provided a practical path for the future development of high-value treatments for waste plastics.