I've had the JAE, MPA, and now KRG C-4.
I'd say the JAE is the "better" of the three, but the C-4 is easier to adjust. The JAE and the C-4 both adjust for height and length, with the C-4 also being able to adjust for angle.
Don't know if MPA has changed anything from the first "adjustable" latch, but it was an absolute POS that looked and operated like an afterthought.