EfficientDet was open sourced March 18 , YOLOv4 came out April 23 , and now YOLOv5 is out only 48 days later.
In our initial look, YOLOv5 is 180% faster, 88% smaller, similarly accurate, and easier to use (native to PyTorch rather thank Darknet) than YOLOv4.
YOLOv4 was published on April 23 with COCO weights, but there haven't yet been resources on how to adapt its architecture to your own domain. This post walks through setting up Darknet and training on a custom dataset in Colab.
FWIW, in our tests, we saw the highest mAP (89.5) on a new task compared to EfficientDet and YOLOv3.