J and L are very similar. One edge the L has are power ailerons, which is nice. I like the J better, not sure why though. Not much to add, to what has been said, except...If you get good at dog fighting, you are going to be a good pilot. Learning the qualities of all planes, will make you better able to get the most out of your plane against other planes.
Bottom line, don't fly something because you think you need to have a better plane. Fly stuff because it is simply fun to fly. The 38 is every bit as capable as any other plane generally speaking. When matched up against a K4, you have got a battle on your hands, but you haven't lost the fight from the beginning....even if equal pilot skills. Mistakes can still be made. I think there are only a few planes that b'n'z is the most viable option, either one of these planes can fight in different fashions, the versatility is a big asset. Though the 109 seems to hold some big edges, the 38 is a fantastic plane in it's own right. It does many things well, but is not the best at anything. If you are a better pilot, there is a good chance you will win. If it's fun, do it.
