The 26/27.
Currently it takes (accounting for traffic) around 45 minutes from Hebburn to Newcastle.
I know in the past an X27 was trialled (and failed) simply because when it's working - the Metro is the only logical option to commute or use for leisure into Newcastle and the Gateshead suburbs,
There are small improvements you could make. If you ran either the 26 or 27 direct from Hebburn Fire Station through Victoria Road East and rejoin the route as is at Station Road you'd shave a decent chunk of time off whilst still leaving Monkton Lane with the 9 or the alternative 26/7.
RE: Go North East: Service Suggestions v2
Wistfully stuck in the 90s