air dry clay v's sculpty

[nzgoddess.livejournal.com]

Id be most appreciative if people could tell me which they prefer and why ??

I'm looking to use it to make dolls faces and possibly some small decorations to be used in mixed media collage work ..

I'd also be interested to know what people find is the best backing for collage .. Even thick cardboard seems to warp when hung on the wall and canvas boards are just so damn expensive - any ideas ?