The standard Traffic Message Channel (TMC) only covers some main routes, while live traffic data (available from TomTom, Garmin, Waze, etc) provides real time traffic info from all roads and streets where drivers use these devices.
The result is that with TMC-only, COMAND always directs me to the main arteries, which in London are usually clogged-up with traffic, while Waze takes me through back streets bypassing the busy main routes.
At rush hour, COMAND will take me to my office using Marylebone Road / Euston Road / City Road, a 1:00h to 1:15h journey, while Waze does it in 35 to 45 minutes through Islington's back streets.
When driving out of town, Waze has less of an advantage because TMC is reasonably OK for Motorways (though Waze does have some additional information about hazards).