"PVC is more flexible than ABS, but ABS is stronger and more shock resistant. ABS is better at handling severely cold temperatures, but it can warp with exposure to direct sunlight."
I've never used ABS but last year I made a PVC rail that slid pretty well until it cracked after a couple sessions. It seems like ABS might be more durable given that it's better at handling cold and is more shock resistant. I'm not sure how it slides or how well it would actually work though.