Thanks for input. What benefits would I see with this router?
It depends where the slowdown is. If its on the outside of your property, then no difference. However if you are getting slowdown due to lots of neighbours using all the WiFi channels available at 2.4GHz, then a dual band router is worthwhile (if your kit can make use of 5GHz - older stuff can't, e.g. iPhone 4/4S and older laptops).
The HomeHub 3 is very competent but only 2.4GHz.
Best way to test is a wired connection to the hub and run a speed test, that is the max you can possibly get.
James BT Infinity 2 19/09/2012 - Sold 42/6, Now 52/9, Sync @ 55 / 9.5 Mbps @ 470m approx
15 years broadband (1999 ntl: cablemodem, BT FTTC) - Router: Asus RT-AC68U (merlin) - Modem: HG612 unlocked Typical speedtest