A neck humbucker pickup, as played by Slash, is not going to sound much like either of your choices based on your current equipment (neck single coil or bridge humbucker).
Think of neck pickups as more bassy and bridge pickups as more trebly, whether or not they are single coil or humbuckers.
Whereas single coil pickups are a bit clearer, thinner. Humbuckers grittier but can also get kind of muddy.
Rather than worry about exactly matching the tone, I would focus on really listening to your instrument and trying to find a tone that YOU like. The bridge pickup with the tone rolled off a bit would probably get you a bit closer, to answer your original question. That way you are getting the grittiness of the humbucker, and with the tone rolled off it's a bit bassier, almost like a neck pickup. I hope this helps.