I'd say the risk from cellular signals is greater than that of wifi due to the signal strength at the emitter source.
Phones themselves have limits to signal strength, measured in power absorbed / mass of tissue:
Specific absorption rate. The EU and US measure SAR slightly differently, but both have set legal SAR limits and most phones emit about half of the legal limit.
Cell phone towers, however...
They do not have limits everywhere. Where I live, there is none but there is practically a
lower limit to them as carriers are required to be able to service an area "sufficiently" to be eligible to do it at all.
Unlike phones, each antenna also emits in a single direction.
Then, not every cell tower is backed with a wire to the network but through a directional microwave link.
Where as with cell phones you have a choice if you want to radiate yourself with them or not, with microwave links and cell phone towers, you don't.