I like fleece the best, and I think its the least smelly. Its, also relatively cheap if you have your own washer and dryer. But it also requires daily work.
So for just toss the stuff in and don't worry about it for a week, Carefresh is the best. I know some places use a combination of shavings, and Carefresh, but quite frankly the piggies still pick up the shavings, which get all over the place. So even though its a bit more expensive, I'd recommend the Carefresh. We use it under our hay racks, and it doesn't get stuck to their paws and fur and make a mess like the shavings do. I'm still finding shavings from the last we used them!:yuck: