YOLOv5x in particular is now above 50.0 mAP at --img-size 640, which may be the first time this is possible at 640 resolution for any architecture I'm aware of (correct me if I'm wrong though).
YOLOv4x got 51.0/50.7 mAP at --img-size 640 in last year.
YOLOv4x got 51.0/50.7 mAP at --img-size 640 in last year.