Oddly enough, but the question is very close to my specialty =) We are researching the biodegradation of polymers in vivo.
The question is actually very complicated. For an accurate answer, you need to conduct an experiment under specific conditions. But we will not conduct such an experiment.
So, if the body is wrapped tightly so that there is no access of air and moisture from the external environment, then such an object will decompose longer. So, only microorganisms "work", if the object is unwound, birds, insects and animals are involved in the case. The film only promotes the biodegradation process by creating a greenhouse effect, which increases the temperature inside. Otherwise, the film only slows down the process. If you use a perforated film or make a perforation yourself, the rate of biodegradation will increase. But, in general, the biodegradation process is likely to be slower in plastic wrap.
What are you up to, Sergey?
In general, the question is posed incorrectly: faster or slower than under what conditions? In addition, it depends on what kind of polyethylene to wrap. After all, it may not be transparent.
The rate of decomposition depends on many factors, and depending on the conditions, this process can take decades.
In soil and water, rotting occurs much more slowly than outdoors. It also slows down in sealed containers, but in the case of containers, humidity and temperature play a greater role.
If we take the dry summer period as the conditions, then the decay process will accelerate, since thanks to polyethylene, favorable for ammonifying microorganisms greenhouse effect (high humidity and temperature). However, in general, the decomposition process will slow down, since access to insects that play a significant role in it will be closed.
In the warm summer period, in a few days, the corpse will literally be covered with larvae of various insects that feed on carrion. Their activity greatly accelerates the decomposition of the body.