Performance comparison with YOLO

[snakeztc]

To my understanding, two-stage detector in general is more accurate than single-stage detector. However for all the pre-trained models listed in ModelZoo, it has lower or similar AP score compared to models in Yolov5. I wonder what contribute to the difference since the pertained models in Detectron 2 are in general more complex and larger. Can anyone explain about this? Thanks!

For example, a big R101-FPN Faster-RCNN model only achieve AP 43, while yolov5x has AP 50.7, which is much smaller and faster.