Yes, there are definitely differences in the quality of the clear stamps. Some appear very flimsy and flop around like a gummy worm<G> and others are more of a thick, solid feel.
You will find that all clear stamps will stain some, so, the turning orange is probably staining. Also, I'm not sure what sets you're using, but, with any clear acrylic stamp, if you press down as hard as you would with a rubber stamp, you're going to squish the image and make your lines thicker. Since the acrylics are softer than rubber, they don't take as much pressure.
Suz
CTMH Director
http://www.suzastampin.com