As I understand it, the main difference is what muscles provide the deceleration. The net effect is supposed to be that the knees suffer from less decelerative stress in a reverse lunge, because they don't have the weight of the body coming behind them when you put your foot down. Instead of stepping forward and planting the foot, weight coming forward into that stepping foot and knee, you step back, touch the toe, and then bend the knee down to the floor.
I'm not certain on this. I know reverse lunges feel easier on my knees than either forward lunges or static lunges, which is why you see so many in my log. The DeFranco's guys love them too, I've seen reverse walking lunges used there but haven't seen many forward lunges.
When I get up tomorrow I'll dig around more and see what else I can find.
So when you reverse lunge, you don't plant the back foot? Just touch the toe and drop the knee? But still, if you step forward, shift the weight to the front leg, roll the back foot up onto the toe, then go down. It still seems to me like it would have the same effect.
The idea of decelerative forces on the front leg I'll have to think about. Maybe I'll just have to do more of both to understand.