Paul has two Dell Laptops, one with an AMD and one with an Intel i5. Both run at the same speed of 2 GHz with 8GB of RAM and running Windows 10. But the download speeds are vastly different. Leo says that different WiFi chipsets could account for a 20% difference, but not the disparity that Paul is seeing. So something is wrong in the networking stack.
Leo suggests trying to do the speed test with a wired ethernet connection and see if the wired speed is the same. If it is, then there's probably a driver issue with the slower machine. Also try using a cheap USB WiFi adapter and see if you can improve the speeds. If so, then you're likely looking at a bad WiFi driver for the slower machine. Update the Intel driver with the Microsoft driver, disabling the Intel one. From the chatroom - https://www.intel.com/content/www/us/en/support/detect.html
Dell also has something called SmartByte, which the chatroom says can slow down your internet speeds. Look in add/remove programs and if it's there, get rid of it. You can disable it with Windows Key + type Services.