Gasification, using it as a fuel makes more sense. Reducing it down to basic carbon constituents. At least in this forum it’s productive and photosynthesis can turn it into organic mater.
If you do incineration right (with pollution controls and energy recovery), simply burning it is more direct.
Gasification is a nice intermediate step if you need to mix it with syngas or natural gas to augment supplies, but if you really just are going to convert to electricity or heat eventually you may as well just do it in one centralized step.
Either way the plastic product is just one stop on the path from hydrocarbon to energy and CO2+H2O, but I do think centralized incineration is more practical (especially since it's already done all over the place) with little real downside.
Just assume as a rough estimate that the gas you'd get from gasification is displacing natural gas production. If you just burn the plastic (and other trash) in a way that prevents serious pollution from getting into the air it's bound to be more efficient to do that and then just burn less natural gas -- versus trying to turn what is essentially already fuel into natural gas substitute.
