I am not familiar with the "ball of the foot jab", the only time I practice it is during kihon and the rare join-dojo practices. My dojo doesn't use it much, I was told it doesn't do enough damage. And from what I've taken - I have to agree.
Ball of the foot jab can be an awesome power kick or a great jab followed by a power kick (like jab - cross from boxing). I've studied Muay Thai for several years and I'm currently studying TKD, both styles can use the front kick very effectively. If you watch boxing you can see how some boxers only use the jab as busy work to setup power shots and others can really knock you out with the jab. The same can be said for TKD and Thai Boxers. I've seen many fighters get knocked out cold by a good front kick or get the wind knocked out of them then get punked by a good round kick. Just my thought and experience.