500grains,

"a" would depend on whether the lead core bullet has a round nose or is an FN as well. If both are FN and both are stabilised to better than SF2, there will be very little to choose between the two. If the lead core bullet is a round nose, it is a no contest, the FN is more reliable.

"b" Penetration depths would be similar if the lead core bullet does not bend. The higher speed of the FN would cause more damage and it would be more reliable - straighter tracking in the animal and less likely to be damaged along the way.

With both a and b the drive band bullet is easier on the bore of the rifle and produces less recoil.

The danger is that monos of equal weight to traditional weights may be too long, if stability factors fall below 2 and speed goes beyond 2400fps, the bullet may be destabilised by the impact. The specification of the cartridge plays a big role. If the twist is fast enough and there is enough case capacity, there is no need to drop in weight when using monos although it is an advantage to do so.