I use the pad. I had to read "That Perfect Stitch" to learn how to use the Roxanne thimble. She recommends the pad of the finger, and once I started using her method my stitches came out better.
Deidre McElroy, Roxanne's daughter, claims that using the top of your finger is ergonomically bad for your hand. I don't know if that's true, but I do know I don't have any hand problems when I quilt.
Janet