Bullet bearing surface (length) does indeed influence velocity. Sometimes this works in strange ways and has much to do with the composition of the bullet...type.hardness of the core, jacket material and thickness and base thickness. Some of the Barnes bullets come to mind here.
All things being equal, it's been my observation that longer bearing surfaces will give more 'effective' chamber pressures than similar weight bullets with a shorter bearing surface.
But it's one of those "It depends" kinda' things, I believe.