I recently got cable internet after being on ADSL2+ for a decade (Australia) and found that my Netgear D7800 Nighthawk router slows down my internet by almost half.
I've done speedtests connecting right to the Cable Modem (Arris CM820) and the much cheaper ISP supplied router (Sagemcom F@ST 3864AC), both give 94mbit down and 38 mbit up compared to the 50mbit down and 38mbit up on my Netgear Nighthawk. For some reason it only affects the download speed and not upload speed.
I've done speedtests connecting right to the Cable Modem (Arris CM820) and the much cheaper ISP supplied router (Sagemcom F@ST 3864AC), both give 94mbit down and 38 mbit up compared to the 50mbit down and 38mbit up on my Netgear Nighthawk. For some reason it only affects the download speed and not upload speed.