If it were me, then I guess I'd choose the 57 as it appears to operate a more direct route down Old Durham Road as opposed to Windy Nook, Felling Square and Deckham. A quick look at the timetables confirms that this is true - the 57 takes 30 minutes between Fewster Square and Newcastle whereas the 58 takes 34 minutes although the 4 minute difference between may be reduced depending on the level of traffic congestion on Old Durham Road towards the QE.
As stated earlier, both buses do not follow the exact same route between Meresyde and Woodburn as there is a slight variation between Staneway and Wealcroft. If we are to ignore that variation then there is approx 1.35 (1.2 vs. 1.5) miles of route and, if included, there is approx 0.9 miles of route which both routes share around Leam Lane Estate. Both routes serve different functions as some residents may travel to the QE while others may want to travel towards Felling Square. Given these considerations and the minimal distance shared (inevitable and unavoidable in some cases), it's hardly worth changing the route in my opinion. I just don't see the point.
RE: Go North East Service Suggestions