Navigon Myroutes is your own historical time of day info (one GPS device). So MyRoutes will only work in places and times that you drive frequently.
Tomtom IQroutes is the historical info of all Tomtom owners who choose to share it. So it's crowd-sourced.
Real time traffic will only help to a point, historical traffic is necessary if a decision point is needed far in advance (eg: when I drive from Boston to NYC, should I take Merritt or 95? should I take Deegan or Cross Bronx? Or when going into DC to I take 95 or 295?, which way do I go around the belt? etc..)
According to Navigon My Routes use historical data in general which is acquired from third party and personal data which allows the navigator to suggest routes which the driver prefers.
Regarding historical data in routing you have point there but as you probably know real time data (live data) is not only live data but also flow data from historical models. The point of "live" navigators is to be able to tap into cloud which holds much more information and computational power then any single navigator could hold. This info holds also the historical data aka flow models combined with real time traffic. Therefore, on live navigators server side info is going to play ever increasing role.