With the smaller ammo package, the L starts with 150 x 20mm rounds, while the J starts with 80. With my (poor) aim, the extra 70 helps. I haven't been playing all that long, so I don't "feel" a difference between the J and the L (although I'm sure there is one).Here is a numeric comparison between the 3 models:http://gonzoville.com/ahcharts/index.php?p1=p38g&p2=p38j&p3=p38l
there isn't an appreciable advantage in taking the light ammo load, it's not going to make you turn any better or win any fights.
The only difference is in overall weight and that much ammo isn't much compared to the p38's base weight. The ammo is also ahead of the Center of Gravity as well and is just a little friendlier in the weight department.
I prefer the L especially the old 38L over the J as it turns just as good and is much better in the vertical.
Hopefully we can prove that the J is lighter, in fact. Then we'll probably have more J pilots popping up.
No difference between the J and the L in the vertical. ack-ack