Hello @Misery99, Thank you for posting in the community.
How do you use these two routers? Were you connecting them directly to the internet modem and doing the tests separately or were you connecting one to the other? Please make sure you're using the same settings, same position, and same direction on both routers when doing a comparison.
Is the speed tested on a wired device or a wireless device? Please try doing the test by connecting a PC to the LAN ports on both routers and check if the wired speed is similar.
Try resetting them both to factory defaults and leaving all settings by default, then just connect them to the internet to test the speed again.