I had the same issue with DD and the pull-up/diaper comparison. She thought they were the same thing, so we only used them for naptime & bedtime until she woke up dry on a consistent basis. We used the vinyl panties for about a week and then went right to the cotton ones (too bulky for my princesa-on-the-move). She used to have about 1 accident a week, but I think that really helped with her training because she knew when one was coming and could tell us right away.
Good luck!
