my ipv6 speeds are slower than ipv4

So I recently just setup ipv6 on my router, but the speeds seem to be lacking compared to ipv4. I'll give some details below of my equipment and service.

Modem: Netgear CM1200

Router: Netgear Nighthawk R7000P

ISP: Comcast - Gigabit

When on ipv6, my xfinity speedtest hits around 657 Mbps. But if I turn off ipv6 (within my windows network adapter), my ipv4 speeds hit around 945 Mbps. I will post more information down below.

Speed test I used: https://speedtest.xfinity.com/

I got 10/10 on this site: https://test-ipv6.com/

And  here are some screenshots of my results, as well as my ipv6 setup within my router.

ipv6 speed test: https://i.gyazo.com/82f846cbcc8881e73d398a61bf7dfc96.png 

ipv4 speed test: https://i.gyazo.com/fe07194cae6aaa8b7a98c0f74baf2053.png 

ipv6 connectivity test: https://i.gyazo.com/73c79d5a4bed8943ca9314e66a09ee6a.png 

Router ipv6 settings: https://i.gyazo.com/c2588e46aa45f28e4e1d239f95b862d3.png 

For my router, I intially had chosen Auto-detect, in which it choose DHCP for me. As you can see, I also changed my DNS to cloudflares 1.1.1.1.

Thanks for any help on this issue.