Advantages of PVC is that it's lighter in weight and easily moved. Gluing larger diameters is tricky, you have to use slower setting glue and really have to force the pieces together, and hold them together until the glue sets. It helps to use a marker to know how far you have to shove the fitting on the PVC pipe. PVC won't rust out like steel.(especially the corrugated stuff)
PVC might or might not have UV inhibitors in it. So, the stuff exposed to the sun might get brittle over time. Some people here have been known to mistake the PVC pipe for a muskrat and shoot it.....

I should say a particular person, as he's the only one that I've known to do it.
If PVC freezes it might split easier than steel pipe. It won't turn rusty brown, so it won't blend into the background as easily.