For Mendip and Wales type of caving a Fleece undersuit and a Cordura oversuit are ideal
For draughty wet Yorkshire type pitches some people prefer the pvc type oversuit (still with a fleece undersuit) but theses are easily subjected to damage and once ripped need careful repair or they will not last very long.
IMHO a good relatively new Cordura suit is as wind and water proof as the PVC suit anyway, and much more robust. (light blue touch paper and stand well back )
Yes Cordura is tough but what about the thread and manufacture? I had a Beaver Cordura suit which used such weak thread that the crotch ripped on the first trip underground! Also the waterproofness does not last at all. You might be grateful of a good waterproof/windproof oversuit while walking across some god-forsaken moor in the p*ssing rain looking for an elusivecave entrance... or hanging around at some exposed shaft-top in winter...
Yes the PVC used in "boil-in-the-bag" suits are more likely to get ripped - but then they are MUCH easier to repair (almost the same as wetsuits used to be!).
Just spread some PVC glue around the tear, apply a patch of the same material (with rounded corners), press down leace to dry and job done. Most PVC suits even come supplied with the patching material and glue.
I've had a number of different oversuits over the years (and started on second-hand boiler suits/old clothes) and I've found that the PVC variety last just as long id not longer than the Cordura tpe. My current PVC oversuit has quite a few patches, espcially in the "derriere" region, but is still going strong after more than three years heavy use (including a week's trip to the caves on Skye!).