Don't know the exact differences but . . .
one thing is for sure,
I fly both very often and the only very important difference I program into my brain before each flight is the following:
Over here at altitude (L4's w/no High Alt. Kit) you will run out of left pedal a lot sooner than you will run out of power (TQ, TOT, N1), learning this has many pilots around here to some nasty surprises. With the L3 if you watch your wind you'll run out about the same time you reach both limits.
I remember there was this really tall building I used to fly out of with a TV crew, and somedays the thing would hover IGE about 12 inches from the ground with 75% TQ, but the left pedal would be almost all the way in, any increase in power would start the nose going right and no pedal to stop it, so in order to clear the pad you had to start pulling pitch 180 deg. from the desired exit, the L4 would climb as it yawed right with the left pedal all the way in, then as I reached the desired heading being now 20-30 feet high, I would lower collective slightly to stop the yaw, and push collective forward until I had some airspeed, needless to say that the aircraft that when the aircraft sank I now had plenty of altitude to clear my tail from the edge of the building.
Returning to the pad heavy was a completely different story, but I guess easier since it requires less power to land than to take off, but you had to have the wind help you.