Vet bed all the way for me
It just makes life so much easier for us as we have 18 piggies so the six pens they live in are hoovered thoroughly twice a day to get hay and poops off. Keeps the piggies warm 24/7, is nice under their little feet and on deep cleaning days, the pieces are rolled up after hoovering and washed then hung up, dry in a day. Rolls can be cut to size as our pens are all 6ft+ and it stays in place and I tuck it up around 4" at the front and back to keep any draughts out so know they are snug and toastie :x
Downside is the amount I have to wash to keep a clean supply and storage but we have a small utility room and my OH put deep shelves and hanging space up for me.
Vet bed can initially sound expensive but if people shop around on ebay, there are some good prices - I buy rolls of 5 or 10m.
Plus side is it keeps the piggies dry as it wicks the wee away so they're not lying on wet bedding and can leave pairs/trios of piggies for a week between changes, lots of lovely colours available but most important, our piggies love it.
Coincidentally, I've not had any illness from a piggy since switching to vet bed, I used a small piece last year when one of my boys was ill to maintain his body heat and decided then it was the best thing and switched to kitting the whole pens with it.