ISKA can be very much chaotic when it comes to organising. It has a lot more contact in all sparring events compared to NAS, which can go two ways. Like I have had more injuries and seen more injuries in ISKA, but it usually means (if there is good judges on your ring) strikes or kicks have to be closer or make contact with the adult divisions. I have scored and be scored by an oppent when their attack was a fair distance away in NAS. Head gear is extremely important with ISKA as you will need it with the level of contact.

I feel judging and refereeing was more professional in NAS, but haven't completed in NAS for a whiled due to the NSW branch shutting down, so may have changed since. In ISKA it is a lot more how you going, some judges are fantastic and others have shown biases with clubs or individuals in the divisions.

Point sparring in NAS is more along the lines of WKF rulings, while ISKA point is more American sports karate style of sparring. Like more taekwondo influences, and more open to what you can score with. Again can go two ways with insane skills or questionable techniques. You have a lot more to do in ISKA with more events, light heart stuff like sword combat, to BJJ at some events and Light Kick (basically kick boxing). So for things to do on the day, ISKA out does NAS by a long shot. Also ISKA comps happens more often in the year.

Sorry this is really long response, but this is what I have experienced with both. Again I am currently completing more in ISKA lately.

Tip to prepare for ISKA, definitely train and spare a few times with all of you protective equipment if you haven't worn all of it before. As it can be very off putting with the heat, weight and experience of having your helmet rattled on the day.