I have had just the opposite, I have had quite a few stripped karbonite gears. I am not a fan of them.The 425 has plastic gears and have never had a problem.(to quantify I have stripped plastic Futaba gears)
Neither the 322 or 425 really completely compare to the 3004 Futaba.
The 425 has just slightly higher torque, better bearing setup, same plastic gears and similar price.
The 322 has similar bearing setup, same torque, karbonite gears and lower price.
Save money with the 322 and get a slightly worse servo (in my opinion) or spend the same money and get a better servo with the 425.