GTX 1060 vs GTX 1660

I have bought two graphics card for custom object detection using yolo-v3.

  1. GTX 1060
  2. GTX 1660
    According to the specification GTX 1660 graphics card is better than GTX 1060.
    But while testing yolo-v3 model GTX 1060 is 5 times faster than GTX 1660.
    To detect object from 1 small image in GTX 1060, it takes 35 millisecond
    To detect object from 1 small image in GTX 1660, it takes 140 millisecond
    I have used CUDA10.0 and CUDNN 7.4 for yolo_cpp_dll.
    According to specification GTX 1660 should be faster than GTX 1060.
    Am i wrong in somewhere please comment.
    Regrads
    Israfil