I would think between $350.00 to $550.00 with the $550.00 being the gun in exceptional condition.
Many like the 41Mag because it is truly .410 and the 44Mag is .429 so it is only lightly smaller than the 44.
The 44 has many more bullets available - 180 , 200 , 210, 220 , 225 , 240, 250 , 265 , 280 and 300 grain.
The 41 has many between 170 to 255 grain available, with 170 and 210 being the most commonly available.
The 41 has slightly less recoil.
The 44 would be a better choice if you do not handload only because of the availability of factory loads.
If you handload it would not matter, the power of both would be very close at any practicle hunting range.
David Carey