I have used corrugated pvc sheets several times, to replace a wooden greenhouse roof originally made of glass firstly because it is possible to overlap the sheets and so no joints are exposed that can leak or cause rotting later. PVC is also very cheap and easy to lay. It is very easy to replace a roof of glass with a pvc roof , simply adding extra support purlins over the original wooden trusses ( i.e. the horizontal pieces across over the wooden ones sloping down the roof.).With care and using a floorboard for support it is possible to walk on the board over a pvc roof; this enables one to replace individual sheets and do maintenance such as adding extra screws.
Pvc roofing does deteriorate and become cloudy after about ten years; but it is so cheap and easy to renew that I think this is worth it.
It should be even easier to build a new greenhouse with pvc corrugated sheets than it is to convert one from glass to pvc. I definitely would not use glass .
The main disadvantage of pvc (and presumably for polycarbonate) is that if a very hot bonfire is lit nearby sometimes cinders drop onto the roof and burn small holes.These do produce drops inside but the effect is not serious. But with care this can be avoided, by keeping fires away .

PVC roof can even be extended over the edge of the walls, by about 12" , so as to protect the wooden sides from rain and rot.This has to be limited by the strength and direction of the prevailing wind. But can be used to good effect if the pvc sheets are anchored securely and supported well.If necessary a double layer of sheeting will help to strengthen this at the overlap edge.

I would say that I'm not as familiar with polycarbonate corrugated sheeting;it seems not be easily available either .I am trying to find out more about it especially whether polycarbonate is better for the quality of light for some greenhouse plants.It may go cloudy more slowly.
I don't find a problem with tomatoes,or sweet peppers or cucumbers which flourish. But my vine - Black Hamburgh- does not do well . Does anyone know more about the horticultural properties of polycarbonate compared to pvc , as well as glass ?