If you are satisfied with JkDefrag, continue using it.
You know the saying: Never change a running system?
Most defraggers do a good job and are able to deal with about 80% of all situations.
I startet looking for a new solution when i want to place my files in a order I
define but the standard defragger. From my point of view the advantage of MyDefrag ist the scripting language. This language allows complex scripts for placeing files in any order you like. I use a laptop with a 2.5" hdd and those hdds are slow. With MyDefrag and my own scripts i am able to sqeeze some speed out of my disk.