With the two degree outer hubs though your also stuck with 2 degrees of toe unless you switch to a 1 degree hub - or you have to sweep the rear arms out. Generally with a foam car you run 1-1.5 degree of toe. So that's something to keep in mind.
The rear hubs also have a smaller bearing. Smaller bearings may not take as much abuse, but they have less rolling resistance so should be faster. If your running rubber I would not worry about it, foam and you will break the fronts which can lead to you eating a CVD, especially in 19T or modified.