Personally, when leading trips down there I wear a thermal top, fleece undersuit and a cordura oversuit. Also, I always have a fleece balaclava with me which I'll wear if hanging around or feeling chilly.
Certainly, it's easier to clean the muck off a PVC oversuit and it might be a little warmer, but it is noticeable how much more friction cordura gives you when thrutching and climbing about in the muddy entrance series - so there is an advantage there! I don't currently own a PVC suit so haven't that option, but if I did, that's probably what I'd wear.
You're really not wet for long in Otter Hole, so I wouldn't think a neofleece worth it if your other kit is in reasonable condition.
Hope that helps!