MDX Load ratings vs AASHTOWARE

Is anyone familiar with AAHTOWARE load rating software? We're looking at a project that requires girder strengthening. Early on, we checked them using MDX; everything was fine. Recently, the owner provide AASHTOWARE input files. Wen we ran them, the ratings are typically 20% lower for LRFD and LFD. We didn't see any input discrepancies between MDX & AASHTOWARE. We don't typically use AASHTOWARE. I haven't used MDX directly for many years, although I've always had doubts about it. I was just wondering if anyone has any insights.