The storm track is really dependent on the degree of confluence up north from pieces of vorticity rotating southeastward into the '50-50' vortex. There is no HP up top to speak of. The key difference imo remains the piece of energy(vorticity lobe) in SE Canada, west of Maine. On the GFS it stretches into a vorticity ribbon as it flows into the gyre, so there isn't as much dig southward as other guidance. The Euro, CMC, and Ukie keep that vort lobe more intact/further south, increasing confluence and acting to suppress the storm track a bit more.